Hourstonius, Hoover & Bousfield, 2001

Lee, Kyung-Sook, 2010, A new species and new record of the Amphilochidae (Crustacea: Amphipoda) from Korea, Zootaxa 2477, pp. 21-36 : 31

Key to the North Pacific Hourstonius species

1. Gnathopod 2, carpal lobe very short; palm transverse .............................................. H. pusilloides (Shoemaker, 1942) Gnathopod 2, carpal lobe long; palm oblique............................................................................................................... 2

2. Gnathopod 2, basis without posterodistal extension..................................................................................................... 3 Gnathopod 2, basis with posterodistal extension.......................................................................................................... 9

3. Gnathopod 2, basis with posterodistal spine; telson, length> 2.3 × width .................................................................. 4 Gnathopod 2, basis with posterodistal seta(e); telson, length <2.1 × width ................................................................ 6

4. Gnathopod 2, propodus with 2 dorsal spines; epimeron 3 with posteroventral cusp ........ H. vilordes ( Barnard, 1962) Gnathopod 2, propodus lacking dorsal spine; epimeron 3 lacking posteroventral cusp.............................................. 5

5. Carpal lobe of gnathopod 2 extending beyond palmar angle, dactyli on gnathopods smooth on inner margin............. ........................................................................................................................................... H. longus ( Hirayama, 1983) Carpal lobe of gnathopod 2 short, not extending beyond palmar angle, dactyli on gnathopods serrate on inner margin ........................................................................................................................................ H. japonica ( Hirayama, 1983)

6. Epimeron 2 with small posteroventral cusp.................................................................................................................. 7 Epimeron 2 lacking posteroventral cusp..................................................................... H. breviculus ( Hirayama, 1983)

7. Antenna 1, peduncular article 2 <article 1; dactyls of pereopods 3–7 simple ............................................................. 8 Antenna 1, peduncular article 2> article 1; dactyls of pereopods 3–7 inner margin with tooth at base of unguis........ .................................................................................................................................................... H. geojeensis sp. nov.

8. Telson, strongly tapering, apically narrowly rounded; maxilliped, mediodistal margin of outer plate incised.............. .................................................................................................................................................. H. pele ( Barnard, 1970) Telson , gently tapering, apically broadly rounded; maxilliped, mediodistal margin of outer plate straight ................. ........................................................................................................................................... H. baciroa ( Barnard, 1979)

9. Telson short, semiovate, not reaching distal end of uropod 2................................................................. .................... 10 Telson very long, reaching distal end of uropod 2................................................ H. robastodentes ( Hirayama, 1983)

10. In female, gnathopod 2 propodus with 2 anteromedial spines; epimeron 3, subquadrate with posteroventral cusp...... ....................................................................................................................... H. oozekii ( Hirayama & Takeuchi, 1993) In female, gnathopod 2 propodus lacking anteromedial spines; epimeron 3, posteroventrally produced without cusp .................................................................................................................................... H. koreana ( Kim & Kim, 1992)