Hyalella 575 



j Dorsal teeth only on the pleon 1. H. sissteea . . . . p. 575 



\ Dorsal teeth on both peraeon and pleon — 3. 



j Side-plates 1 — ^4 apically acute — 4. 



I Side-plates 1-4 not apically acute — 5. 



I Peraeon segments with lateral teeth 



\ Peraeon segments without lateral teeth 



t Dorsal teeth large, present on all peraeon segments 

 ] Dorsal teeth small, not present on peraeon seg- 

 l ments 1—4 — 6. 



IGrnathopod 2 in <5, 6*^ Joint broader than long, 

 palm defined by a tooth 5. H. latimana . . p. 577 

 Gnathopod 2 in (5, 6tli Joint longer than broad, 

 palm undefined 6. H. longipalma . p. 577 



{Side-plates I —4 produced into spine-like processes 7. H. armata . . . p. 577 

 Side-plates 1 — 4 not produced into spine-like pro- 

 cesses — 8. 

 I Without accessory branchiae (so far as known) — 9. 

 \ With accessory branchiae — 11. 



{Uropod 3 nearly reaching end of uropod 2 . . . 8. H. longistila . . p. 577 

 Uropod 3 not nearly reaching end of uropod 2 — 10. 



f Stout, with coppery lustre 9. H. cuprea . . . p. 578 



\ Not stout, without coppery lustre 10. H. inermis . . . p. 578 



{Gnathopod 2 in cj, finger closing strongly on inner 

 surface of 6th Joint 11. H. jelskii. . . . p. 578 

 Gnathopod 2 in (5, finger with apex only on inner 

 surface of 6Wi Joint - 12. 

 Peraeopod 1 shorter than peraeopod 2 — 13. 

 Peraeopod 1 not shorter than peraeopod 2 — 14. 



Maxiila 1, palp comparatively long 12. H. dyboTvskii . p. 579 



Maxiila 1, palp very short 13. H. lubomlrskii . p. 579 



Gnathopod 2 in (5, hind margin of 6*^ Joint apically 



bulging, in $ 6tJi Joint not apically widened . 14. H. meinerti . . p. 579 

 Gnathopod 2 in cJ, hind margin of 6*^ Joint not 

 ^ apically bulging, in $ 6tli Joint apically widened 15. H. "warmingi . . p. 580 



1. H. azteca (Sauss.) ?1818 Ampithoe dentata, Say in: J. Ac. Philad., v. In 

 p. 383 I 1874 Hyalella d., S. I. Smith in: Kep. U. S. Fish Comm., v.2 p. 645 t. 2 f. 8—10 | 

 1876 Alien-ehestes dentatus, Faxon in: Bull. Mus. Harvard, v.B p. 373 | 1858 Amphitoe 

 aztecus, Saussure in: Mem. Soc. Gen^ve, v.l4ii p. 474 t. 5 f. 33 | 1888 Hyalella azteca, 

 T. Stebbing in: Rep. Voy. Challenger, «;. 29 p. 311 ) 1862 ? Allorchestes knickerbockeri -\- 

 Amphithoe a., Bäte, Cat. Amphip. Brit. Mus., p. 36 t. 6 f. 1 ; p. 250 | ? 1877 Lockingtonia 

 fluvialis, Harford in : P. Calif. Ac, v. 7 p. 54. 



Body slightly compressed, pleon segments 1 and 2 each produced in- 

 to a dorsal tooth, usually well marked, but apparently sometlmes obsolescent. 

 Side-plates 1 — 4 almost rectangular. Pleon segment 3, postero-lateral corners- 

 subquadrate. Eyes nearly round. Antenna 1, flagellum rather longer than 

 peduncle, 7 — 9-jointed. Antenna 2 a little longer, ultimate and penultimate 

 joints of peduncle long, subequal, flagellum little longer than peduncle, 

 8 — 12-joiuted. Gnathopod 1 small and slender, palm transverse, nearly 

 straight, defined by a small tooth, behind which apex of finger closes. Gnatho- 

 pod 2 in ö, 6**1 Joint very stout, a little longer than broad, palm oblique, 

 slightly convex, with abrupt notch near middle and 2 slight emarginations near 

 defining angle ; finger stout, curved. Gnathopod 2 in Q weak and slender, 5*^ and 

 6**^ joints long, naiTOw, 6*^ more than twice as long as broad, hind margin 



10 

 11 

 12 



13 

 14 



