Head without eyes, rostrum short, inferior antennal sinus distinct. Pleonites 1–3 with dorsal setae, lacking processes. Urosomite 2 with dorsal robust setae. Antenna 1 longer than antenna 2; accessory flagellum three- or four-articulate. Male antenna 2 with calceoli. Mandible with triturative molar with seta; left incisors five- or six-dentate; left lacinia mobilis four- or five-dentate; palp article 3 with A-, D- and E-setae. Maxilla 1 with inner plate bearing plumose setae; outer plate with 11 serrate robust setae. Inner plate of maxilla 2 with oblique row of facial setae. Gnathopods subchelate. Coxa of pereopod 4 with posterior concavity. Coxal gills with stalks, on gnathopod 2 and pereopods 3–6. Uropod 1 with basofacial robust setae on peduncle. Uropod 3 with small, scale-like inner ramus; outer ramus one- or two-articulate. Telson cleft with apical robust setae.

Neoniphargus (Eoniphargus) kojimai Uéno, 1955, original designation.

Eoniphargus is morphologically similar to Octopupilla in the presence of pleonites without dorsal processes, five-dentate incisor of the left mandible, mandibular palp article 3 with A-setae, inner plate of maxilla 2 with oblique row of facial setae, stalked coxal gills, peduncle of uropod 1 with basofacial robust setae, and telson lobes tapering distally. However, Eoniphargus differs from Octopupilla in the following features (features of Octopupilla in parentheses): eyes absent (rudimentary eyes), incisor of right mandible five- to six-dentate (four-dentate), inner lobes of the lower lip absent (vestigial), and inner ramus of uropod 3 shorter than 0.3 × the outer ramus (0.7 ×). Eoniphargus also resembles Indoniphargus Straškraba, 1967, but the familial affiliation of the latter has been controversial. Tomikawa et al. (2007) and Fišer et al. (2013) included Indoniphargus in Mesogammaridae. Sidorov et al. (2018) regarded Indoniphargus as a member of Austroniphargidae Iannilli, Krapp, & Ruffo, 2011. However, since the taxonomic position of Indoniphargus is beyond the scope of this paper, it will not be discussed here further. Eoniphargus is distinguished from Indoniphargus by the presence of facial setae in an oblique row of the inner plate of maxilla 2 (absent in Indoniphargus) and the elongate propodi of gnathopods 1 and 2 (mitten-form in Indoniphargus).

Holotype: ♂ 4.3 mm (NSMT-Cr 16652), Seto River (34.880555°N, 138.218888°E), Terajima, Fujieda, Shizuoka Prefecture, Japan, collected by T. Torii on 3 June 2004. Paratypes:2 ♀♀, 4.6 mm and 4.3 mm (NSMT-Cr 16653 and 16654), data same as for the holotype.

Urosomite 3 without dorsal setae. Epimeral plates 2–3 without ventral setae. Peduncular article 1 of antenna 1 with robust seta on posterodistal corner. Antenna 2 with peduncular article 2 gland cone not exceeding end of article 3; calceoli present in male. Mandible with 5-dentate left incisor; left lacinia mobilis 4-dentate, right one bifid with three or four teeth. Inner plate of maxilla 1 with six plumose setae. Inner plate of maxilla 2 with seven facial seta in oblique row. Peduncle of pleopod 3 with seta. Uropod 1 with peduncle bearing basofacial robust setae. Uropod 3 with inner ramus 0.3 times as long as outer ramus; outer ramus two-ariticulate, with plumose setae on medial margin. Telson length 1.1 times width, cleft for 67% of length.

The new species is named after Dr. Takaaki Torii, who collected the species.

Male holotype, NSMT-Cr 16652. Head (Fig. 2A) as long as pereonites 1 and 2 combined; eyes absent; inferior antennal sinus distinct with rounded angle. Dorsal margins of pleonites 1–3 (Figs 2A, 5A–C) each with four setae. Epimeral plates 1–3 (Figs 2A, 5N–P) with weakly pointed posterodistal corners; ventral margins without setae; posterior margins of plates 1–3 with one, zero, one seta, respectively. Dorsal margins of urosomites 1 and 2 with robust seta, urosomite 3 dorsally bare.

Antenna 1 (Figs 2A, 3A) length 0.6 times as long as body; length ratio of peduncular articles 1–3 in 1.0 : 0.8 : 0.4; posterodistal corner of peduncular article 1 with robust seta; accessory flagellum three-articulate (Fig. 3B); primary flagellum with approximately 22 articles, each article with one aesthetasc (Fig. 3C). Antenna 2 (Figs 2A, 3D) length 0.6 times as long as antenna 1; peduncular article 4 length 0.9 times as long as article 5; right peduncular article 5 with calceoli, left one lacking calceoli; flagellum 16-articulate, with calceoli (Fig. 3E).

Upper lip (Fig. 2B) with rounded apical margin bearing fine setae. Mandibles (Fig. 2C–E) with left and right incisors comprising five and five–six teeth, respectively; left lacinia mobilis comprising four teeth, right lacinia mobilis bifid with three teeth; molar process triturative with plumose seta; length ratio of palp articles 1–3 in 1.0 : 2.4 : 1.9; palp article 1 without setae; palp article 2 with eight marginal setae; palp article 3 with pair of A-setae, many D-setae and E-setae, lateral face with fine setae. Lower lip (Fig. 2G) lacking inner lobes; outer lobes broad, shoulder rounded, with fine setae. Maxilla 1 (Fig. 2H–J) with triangular inner lobe, bearing six plumose setae on medial margin; outer plate rectangular, with 11 serrate robust setae apically; palp 2-articulate, article 1 without setae, article 2 with six robust setae apically. Maxilla 2 (Fig. 2K) with inner plate bearing seven plumose setae in oblique row. Maxilliped (Fig. 2L–O) with inner plate reaching end of palp article 1, subquadrate, bearing three subapical robust setae and medial robust seta; outer plate ovate, reaching middle of palp article 2, with row of robust setae along apical to medial margins; palp 4-articulate, article 2 longest with medial setae, nail of article 4 distinct.

Gnathopod 1 (Fig. 3J, K) with subquadrate coxa bearing setae along anterior to ventral margins; anterior and posterior margins with long setae; carpus length 0.9 times as long as length of propodus and 1.5 times width of carpus; propodus length 1.9 times width, palmar margin weakly serrate, oblique, with three medial and two lateral robust setae; dactylus not reaching posterodistal corner of propodus. Gnathopod 2 (Fig. 3L, M) with coxa expanded proximally bearing setae along anterior to ventral margins; posterior margin of basis with long setae; carpus length 1.2 times as long as length of propodus and 2.8 times width of carpus; propodus length 2.4 times width, palmar margin weakly serrate, almost vertical, with two medial and two lateral robust setae; dactylus not reaching posterodistal corner of propodus.

Pereopod 3 (Fig. 4A, B) with subquadrate coxa, proximally expanded, bearing setae along anterior to ventral margins; posterior margin of basis with long setae. Pereopod 4 (Fig. 4D, E) with coxa bearing setae along anterior to ventral margins, posteroproximally concave; posterior margin of basis with long setae. Pereopod 5 (Fig. 4G, H) with bilobed coxa bearing seta on anterior and posterior lobes; anterior margin of basis with robust setae, posterodistal corner weakly lobate. Pereopod 6 (Fig. 4J, K) with bilobed coxa bearing seta on posterior lobe; basis ovate, with robust setae on anterior margin, posterodistal corner weakly lobate. Pereopod 7 (Fig. 4M) with subtriangular coxa bearing seta on posterior margin; basis elliptical, with robust setae on anterior margin, posterodistal corner weakly lobate.

Coxal gills (Figs 3L, 4A, D, G, J) ovate with stalks on gnathopod 2 and pereopods 3–6.

Pleopods 1–3 (Fig. 5G–K) with peduncles longer than rami, bearing distal seta on pleopod 2 and proximal seta on pleopod 3; retinacula paired (Fig. 5H); mediobasal margin of inner ramus with bifid plumose setae (Fig. 5I); rami well developed.

Uropod 1 (Fig. 5R) with peduncle bearing three basofacial robust setae and dorsal robust setae; inner ramus length 0.7 times as long as peduncle, with two medial and one lateral robust setae, and ventroproximal robust seta; outer ramus length 0.9 times as long as inner ramus, with two robust setae on medial margin. Uropod 2 (Fig. 5S) with peduncle bearing dorsal robust setae; inner ramus length 0.8 times as long as peduncle, bearing two medial robust setae and two ventroproximal slender setae; outer ramus length 0.6 times as long as inner ramus, without marginal setae. Uropod 3 (Fig. 5U, V) with peduncle length 0.3 times as long as outer ramus, bearing bent robust setae on distal edge; inner ramus length 0.3 times as long as outer ramus, with two robust setae on medial margin; outer ramus 2-articulate, proximal article with plumose setae on medial margin and robust setae on medial and lateral margins, terminal article length 0.3 times as long as proximal article with subapical setae.

Telson (Fig. 5X) length 1.1 times width, each lobe with two lateral and three apical robust setae and two dorsolateral penicillate setae, cleft for 67%.

Female paratype, NSMT-Cr 16653. Antenna 1 (Fig. 3F–H) with peduncles 1–3 of which length ratio in 1.0 : 0.8 : 0.5; accessory flagellum 4-articulate (Fig. 3G). Antenna 2 (Fig. 3I) without calceoli.

Incisor of right mandible 6-dentate (Fig. 2F); right lacinia mobilis 4-dentate, weakly bifid. Apical robust setae of inner plate of maxilliped stiffer than those of male (Fig. 2P).

Gnathopod 1 (Fig. 3N, O) with carpus length 1.8 times width; length of propodus 2.0 times width; dactylus reaching posterodistal corner of propodus. Gnathopod 2 (Fig. 3P, Q) with dactylus reaching posterodistal corner of propodus.

Brood plates (Figs 3P, 4I) narrow, lacking setae, on gnathopod 2 and pereopods 3–5.

Peduncles of pleopods 1 and 3 with three and one setae, respectively (Fig. 5L, M).

Uropod 2 (Fig. 5T) with inner ramus bearing two medial and one lateral robust setae; outer ramus with medial robust seta. Uropod 3 (Fig. 5W) with terminal article of outer ramus length 0.2 times as long as proximal article.

Telson (Fig. 5Y) as long as wide, cleft for 71%.

The species is known only from its type locality in the Seto River, Shizuoka Prefecture, Japan. Specimens were collected at a depth of 20 cm, from the bank of the river.

Eoniphargus toriii sp. nov. is similar to E. kojimai and E. iwataorum sp. nov., with a head bearing deep antennal sinus, antenna 1 peduncular article 1 with a robust seta on the posterodistal corner, antenna 2 peduncular article 2 with a gland cone not exceeding peduncular article 3, uropod 1 peduncle with basofacial robust setae, and uropod 3 with 2-articulate outer ramus. However, E. toriii sp. nov. differs from E. kojimai and E. iwataorum sp. nov. in the following features: right mandible with lacinia mobilis bearing three or four teeth (more than four teeth in E. kojimai and E. iwataorum sp. nov.) and maxilla 1 having six medial setae on the inner plate (eight medial setae in E. kojimai and E. iwataorum sp. nov.).

Holotype: ♀ 5.6 mm (NSMT-Cr 30782), Sabi River (36.898181°N, 140.012153°E), Imaizumi, Ohtawara, Tochigi Prefecture, Japan, collected by Y. Iwata on 27 January 2019. Paratype: ♀ 5.3 mm (NSMT-Cr 30783; G1751), ♀ 6.0 mm (NSMT-Cr 30784), data same as for the holotype.

Urosomite 3 without dorsal setae. Epimeral plates 2–3 each with ventral robust seta. Peduncular article 1 of antenna 1 with robust seta on posterodistal corner. Antenna 2 with peduncular article 2 gland cone not exceeding end of article 3. Mandible with 5-dentate left incisor; left lacinia mobilis 4-dentate, right one bifid with many teeth. Inner plate of maxilla 1 with eight plumose setae. Inner plate of maxilla 2 with seven facial seta in oblique row. Peduncle of pleopod 3 with seta. Uropod 1 with peduncle bearing basofacial robust setae. Uropod 3 with inner ramus 0.25 times as long as outer ramus; outer ramus 2-ariticulate, with plumose setae on medial margin. Telson almost as long as width, cleft for 67% of length.

The specific epithet was derived from the names of Mr. Yasuyuki Iwata and Mr. Tomofumi Iwata, who collected the specimens of this new species.

Female holotype, NSMT-Cr 30782. Head (Fig. 6A) as long as pereonites 1 and 2 combined; eyes absent; inferior antennal sinus distinct with rounded angle. Dorsal margins of pleonites 1–3 (Fig. 6B–D) each with four setae. Posterodistal corners of epimeral plates 1–3 (Fig. 6E–G) weakly produced; ventral margin of epimeral plate 1 without setae, epimeral plates 2 and 3 each with ventral robust seta; posterior margins of epimeral plates 1–3 each with two setae. Dorsal margin of urosomite 1 (Fig. 6H) with slender setae; urosomite 2 (Fig. 6I) with dorsal robust setae; urosomite 3 (Fig. 6J) without dorsal setae.

Antenna 1 (Fig. 6K) length 0.25 times as long as body; length ratio of peduncular articles 1–3 in 1.0 : 0.8 : 0.4; posterodistal corner of peduncular article 1 with robust seta; accessory flagellum 4-articulate; primary flagellum 27-articulate. Antenna 2 (Fig. 6L) length 0.7 times as long as antenna 1; peduncular article 4 slightly shorter than article 5; flagellum 22-articulate; calceoli absent.

Upper lip (Fig. 6M) with rounded apical margin bearing fine setae. Mandibles (Fig. 6N–P) with left and right incisors comprising five and six teeth, respectively; left lacinia mobilis comprising four teeth, right lacinia mobilis bifid with many teeth; molar process triturative with plumose seta; length ratio of palp articles 1–3 in 1.0 : 2.0 : 1.5; palp article 1 without setae; palp article 2 with eight marginal setae; palp article 3 with pair of A-setae, several D-setae and E-setae, lateral face with fine setae. Lower lip (Fig. 6Q) lacking inner lobes; outer lobes broad, shoulder rounded, with fine setae. Maxilla 1 (Fig. 6R, S) with elliptical inner lobe, bearing eight plumose setae on medial margin; outer plate rectangular, with 11 serrate robust setae apically; palp 2-articulate, article 1 without setae, article 2 with five robust setae and slender plumose seta apically. Maxilla 2 (Fig. 6T) with inner plate bearing seven plumose setae in oblique row. Maxilliped (Fig. 7A–C) with inner plate exceeding end of palp article 1, subquadrate, bearing three subapical robust setae and medial robust seta; outer plate ovate, reaching middle of palp article 2, with row of robust setae along apical to medial margins; palp 4-articulate, article 2 longest with medial setae, nail of article 4 distinct.

Gnathopod 1 (Fig. 7D, E) with subquadrate coxa bearing setae along anterior to ventral margins; anterior and posterior margins of basis with long setae; carpus length 0.9 times as long as length of propodus and 1.4 times width of carpus; propodus length 1.7 times width, palmar margin weakly serrate, oblique, with three medial and one lateral robust setae; dactylus reaching posterodistal corner of propodus. Gnathopod 2 (Fig. 7F, G) with coxa expanded proximally bearing setae along anterior to ventral margins; posterior margin of basis with long setae; carpus length 1.2 times as long as length of propodus and 2.8 times width of carpus; propodus length 2.2 times width, palmar margin weakly serrate, almost vertical, with two medial and two lateral robust setae; dactylus reaching posterodistal corner of propodus.

Pereopod 3 (Fig. 7H, I) with subquadrate coxa, proximally expanded, bearing setae along anterior to ventral margins; posterior margin of basis with long setae. Pereopod 4 (Fig. 7J) with coxa bearing setae along anterior to ventral margins, posteroproximally concave; posterior margin of basis with long setae. Pereopod 5 (Fig. 7K) with bilobed coxa bearing seta on posterior lobe; anterior margin of basis with robust setae, posterodistal corner weakly lobate. Pereopod 6 (Fig. 7L) with bilobed coxa bearing seta on anterior and posterior lobes; basis with robust setae on anterior margin, posterodistal corner weakly lobate. Pereopod 7 (Fig. 8A–C) with elliptical basis bearing robust setae on anterior margin, posterodistal corner weakly lobate.

Coxal gills (Fig. 8D, E) ovate with stalks on gnathopod 2 and pereopods 3–6.

Pleopods 1–3 (Fig. 8F–I) with peduncles longer than rami, bearing distal seta on pleopods 1 and 2 and proximal seta on pleopod 3; retinacula paired (Fig. 8I); mediobasal margin of inner ramus with bifid plumose setae; rami well developed.

Uropod 1 (Fig. 8J) with peduncle bearing three basofacial robust setae and dorsal robust setae; inner ramus length 0.7 times as long as peduncle, with two medial and one lateral robust setae, and ventroproximal seta; outer ramus length 0.9 times as long as inner ramus, with two robust setae on medial margin. Uropod 2 (Fig. 8K) with peduncle bearing dorsal robust setae; inner ramus as long as peduncle, bearing two medial robust setae and ventroproximal slender seta; outer ramus length 0.7 times as long as inner ramus, without marginal setae. Uropod 3 (Fig. 8L) with peduncle length 0.3 times as long as outer ramus, bearing robust setae on distal edge; inner ramus length 0.2 times as long as outer ramus, with seta on medial margin; outer ramus 2-articulate, proximal article with plumose setae on medial margin and robust setae on medial and lateral margins, terminal article length 0.2 times as long as proximal article with subapical setae.

Telson (Fig. 8M) length slightly shorter than wide, each lobe with two lateral and three apical robust setae and two dorsolateral penicillate setae, cleft for 67%.

The species is known only from its type locality in the Sabi River, Tochigi Prefecture, Japan.

Eoniphargus iwataorum sp. nov. is similar to E. kojimai but differs from the latter in the following features (features of E. kojimai in parentheses): urosomite 3 without robust setae on dorsal margin (bearing robust setae), maxilla 2 with inner plate bearing seven setae in oblique row (nine setae), and uropod 2 without robust seta on lateral margin of outer ramus (bearing robust seta).

♀ 6.3 mm (NSMT-Cr 30785, G1905), ♂ 4.8 mm (NSMT-Cr 30786), Mamashita Spring (35.680066°N, 139.428283°E), Kunitachi, Tokyo, Japan, collected by K. Tomikawa on 25 June 2016. ♀ 5.0 mm (NSMT-Cr 30787, G 1930), ♀ 4.5 mm (NSMT-Cr 30788, G 1931), Hinochūōtoshokan Spring (35.655783°N, 139.382133°E), Hino, Tokyo, Japan, collected by K. Tomikawa on 25 June 2016.

Urosomite 3 with dorsal robust setae. Epimeral plates 2–3 each with ventral robust seta. Peduncular article 1 of antenna 1 with robust seta on posterodistal corner. Antenna 2 with peduncular article 2 gland cone not exceeding end of article 3; calceoli present in male. Mandible with 5- or 6-dentate left incisor; 4- or 5-dentate left lacinia mobilis, right one bifid with many teeth. Inner plate of maxilla 1 with eight plumose setae. Inner plate of maxilla 2 with nine facial seta in oblique row. Peduncle of pleopod 3 without seta. Uropod 1 with peduncle bearing basofacial robust setae. Uropod 3 with inner ramus 0.25 times as long as outer ramus in female and 0.27 times in male; outer ramus 2-ariticulate, with plumose setae on medial margin. Telson length 0.9 times width, cleft for 69% of length.

Female (NSMT-Cr 30785). Head (Fig. 9A) as long as pereonites 1 and 2 combined; eyes absent; inferior antennal sinus distinct with rounded angle. Dorsal margins of pleonites 1–3 (Fig. 9B–D) each with 4 setae. Posterodistal corners of epimeral plates 1–3 (Fig. 9E–G) weakly produced; ventral margin of epimeral plate 1 without setae, epimeral plates 2 and 3 each with ventral robust seta; posterior margins of epimeral plates 1–3 each with two setae. Dorsal margin of urosomite 1 (Fig. 9H) with slender setae and robust seta; urosomites 2 and 3 (Fig. 9I, J) with pair of dorsal robust setae.

Antenna 1 (Fig. 9K) length 0.22 times as long as body; length ratio of peduncular articles 1–3 in 1.0 : 0.8 : 0.4; posterodistal corner of peduncular article 1 with robust seta; accessory flagellum 4-articulate; primary flagellum 26-articulate. Antenna 2 (Fig. 9L) length 0.6 times as long as antenna 1; peduncular article 4 length 0.9 times as long as article 5; flagellum 13-articulate; calceoli absent.

Upper lip (Fig. 9M) with rounded apical margin bearing fine setae. Mandibles (Fig. 9N–P) with left and right incisors comprising five and six teeth, respectively; left lacinia mobilis comprising four teeth, right lacinia mobilis bifid with many teeth; molar process triturative with plumose seta; length ratio of palp articles 1–3 in 1.0 : 2.3 : 1.7; palp article 1 without setae; palp article 2 with nine marginal setae; palp article 3 with pair of A-setae, several D-setae and three E-setae, lateral face with fine setae. Lower lip (Fig. 9Q) lacking inner lobes; outer lobes broad, shoulder rounded, with fine setae. Maxilla 1 (Fig. 9R, S) with subtriangular inner lobe, bearing eight plumose setae on medial margin; outer plate rectangular, with 11 serrate robust setae apically; palp 2-articulate, article 1 without setae, article 2 with three robust setae and slender plumose seta along apically to medial margins. Maxilla 2 (Fig. 9T) with inner plate bearing nine plumose setae in oblique row. Maxilliped (Fig. 10A–C) with inner plate exceeding end of palp article 1, subquadrate, bearing three subapical robust setae and medial robust seta; outer plate ovate, reaching middle of palp article 2, with row of robust setae along apical to medial margins; palp 4-articulate, article 2 longest with medial setae, nail of article 4 distinct.

Gnathopod 1 (Fig. 10D, E) with subquadrate coxa bearing setae along anterior to ventral margins; anterior and posterior margins of basis with long setae; carpus length 1.1 times as long as length of propodus and 1.7 times width of carpus; propodus length 1.9 times width, palmar margin weakly serrate, oblique, with three medial and two lateral robust setae; dactylus almost reaching posterodistal corner of propodus. Gnathopod 2 (Fig. 10F, G) with coxa expanded proximally bearing setae along anterior to ventral margins; posterior margin of basis with long setae; carpus length 1.2 times as long as length of propodus and 3.3 times width of carpus; propodus length 2.8 times width, palmar margin weakly serrate, almost vertical, with two medial and one lateral robust setae; dactylus reaching posterodistal corner of propodus.

Pereopod 3 (Fig. 10H, I) with subquadrate coxa, proximally expanded, bearing setae along anterior to ventral margins; anteroproximal and posterior margins of basis with long setae. Pereopod 4 (Fig. 10J) with coxa bearing setae along anterior to ventral margins, posteroproximally concave; anteroproximal and posterior margins of basis with long setae. Pereopod 5 (Fig. 10K) with bilobed coxa bearing seta on anterior and posterior lobes; anterior margin of basis with robust setae, posterodistal corner weakly lobate. Pereopod 6 (Fig. 11A) with bilobed coxa bearing two setae on posterior lobe; basis with robust setae on anterior margin, posterodistal corner weakly lobate. Pereopod 7 (Fig. 11B) with elliptical basis bearing robust setae on anterior margin, posterodistal corner weakly lobate.

Coxal gills (Fig. 11G) ovate with stalks on gnathopod 2 and pereopods 3–6.

Pleopods 1–3 (Fig. 11C–F) with peduncles longer than rami, bearing distal seta on pleopod 1; retinacula paired (Fig. 11D); mediobasal margin of inner ramus with bifid plumose setae; rami well developed.

Uropod 1 (Fig. 11I) with peduncle bearing three basofacial robust setae and dorsal robust setae; inner ramus length 0.6 times as long as peduncle, with two medial robust setae and two ventroproximal setae; outer ramus length 0.9 times as long as inner ramus, with two medial and one lateral robust setae. Uropod 2 (Fig. 11J) with peduncle bearing dorsal robust setae; inner ramus as long as peduncle, bearing two medial and one lateral robust setae; outer ramus length 0.7 times as long as inner ramus, with lateral robust seta. Uropod 3 (Fig. 11K) with peduncle length 0.3 times as long as outer ramus, bearing robust setae on distal edge; inner ramus length 0.3 times as long as outer ramus, with seta on medial margin; outer ramus 2-articulate, proximal article with plumose setae on medial margin and robust setae on medial and lateral margins, terminal article length 0.2 times as long as proximal article with subapical setae.

Telson (Fig. 11L) length slightly shorter than width, each lobe with two lateral and three apical robust setae, and two dorsolateral and 1 subapical penicillate setae, cleft for 69%.

Male (NSMT-Cr 30786). Antenna 1 (Fig. 12A) length 0.24 times as long as body length; accessory flagellum 3-articulate; primary flagellum 25-articulate. Antenna 2 (Fig. 12B) length 0.6 times as long as antenna 1; peduncular article 4 length 0.8 times as long as peduncular article 5; peduncular article 5 and flagellum with calceoli (Fig. 12C); flagellum 16-articulate. Gnathopod 1 (Fig. 12D, E) with carpus length 1.2 times as long as length of propodus and 1.6 times width of carpus; propodus length 1.5 times width. Gnathopod 2 (Fig. 12F, G) with carpus length 1.1 times as long as length of propodus and 2.3 times width of carpus; propodus length 2.2 times width, palmar margin with two medial and two lateral robust setae. Uropod 3 (Fig. 12H) with peduncle length 0.4 times as long as outer ramus, peduncle bearing bent robust setae on distal edge.

This species has been found in interstitial waters in Tokyo: the sand-filter bed of the Komae Purification Plant near the Tama River (Uéno 1955); two springs — Mamashita Spring, Kunitachi and Hinochūōtoshokan Spring, Hino (this study).

The present specimens conform with the original description of E. kojimai by Uéno (1955). However, our specimens differed from the original description in the left mandible with 4-dentate lacinia mobilis and maxilla 1 with 11 serrate robust setae on the outer plate, which was 6-dentate incisor and 5-dentate lacinia mobilis of the left mandible, and 10 serrate robust setae in Uéno’s (1955) description. The exact number of these setae is difficult to ascertain because they are minute and overlap. This suggests that he may have misstated the number of setae. Unfortunately, the type specimen of this species is believed to be lost (Tomikawa et al. 2007), so the character could not be verified. Examination of the present material from Kunitachi and Hino, Tokyo revealed some features that were not mentioned in the original description: maxilla 2 with inner plate bearing nine plumose setae in oblique row, uropod 1 peduncle with facial robust setae, and maxilliped inner plate with three subapical robust setae and medial robust seta.