

466 BULLETIN OF THE BUREAU OF FISHERIES. 



Key to the genera of Gam/maridea. 



A. Eyes four, sometimes apparently only two t Hnploops), each with a simple lens (Ampeliscidse). 



Terminal uropods extending much beyond the others; telson oblong, deeply clefl Ampelisca, p. 479 



Terminal uropods extending but little beyond the others; telson short and broad, not deeply cleft Byblis, p. 482 



AA. Two compound eyes, or, rarely, the eyes rudimentary or absent. 

 B. First antennae much shorter than the second; mandibles devoid of a palp; terminal uropods with a single 

 uniarticulate ramus (Orebestiidse). 



C. First antenna' exceeding the tip of the peduncle of the second pair: aquatic forms Allorchestes, p, 47:J 



CC. First antennas much shorter than the peduncle of the second; terrestrial forms. 



First gnathopods in both sexes subchelate Orchestia, p. 469 



First gnathopods simple in the female Talorchestia, p. 468 



BB. Without the combination of characters of B. 

 C. First two pairs of paneopods devoid of spinning glands. 

 D. Last pair of pereeopods much longer than the preceding ones, with the dactyl very long and styliform; 

 eyes nearly contiguous above, near the end of the projecting front ((Edicerida?). 



Carpus of the anterior gnathopods devoid of a prominent posterior lobe Parcediceros, p. 487 



Carpus of the anterior gnathopods prolonged into a long lobe which extends behind 



the hand Monoculodes, p. 487 



DD. Without all the characters of D. 

 E. Rostrum produced into a hood over the antenna:-. Penultimate pera^opods much longer than the last 

 pair (Phoxocephalida?). 



F. Palp of the first maxillae two-jointed Harpinia, p. 478 



FF. Palp of the first gnathopml- ..ne .i Minted. 



Second gnathopods markedly larger than the first PHOXOCEPHALUS, p. 177 



First and second gnathopods of equal size Paraphoxus, p. 477- 



EE. Rostrum not as in E. 

 F. Mandibles not denticulated; palp three-jointed; first antenna 1 with a short, thick base and a secondary 

 fiagellum; coxal plates deep; second gnathopods elongated, slender, flexible, with the ischium 

 elongated and the hand small and furnished with dense patches of short sets; dactyl rudimentary 

 (Lysianassidae). 



G. Telsi m enti re Lysiam »psis, j .. 475 



GG. Telson deeply cleft. 



H. Postero-lateral angle of the third abdominal segment not produced Tryphosa, p. 473 



II II. Postero-lateral angle of the third abdominal segment produced into a small tooth Hoplonyx, p. 474 



II H II. Postero-lateral angle of third abdominal segment produced into a large upturned tooth, above 

 which is a deep marginal sinus. 

 Basal joints of first antenna:- distally produced above; secondary fiagellum small. .Hippomedon, p. 473 



Basal joints of first antenna? not so produced; secondary fiagellum well developed Anonyx, p. 47^ 



FF. Without the combination of characters of F. 

 G. Terminal uropods with a single ramus. 



H. Ramus of terminal uropods one jointed; first gnathopods massive, the second small Unciola, p. 520 



HH. Ramus of terminal uropods two-jointed (Stenothoidse). 



Mandibles with a palp Metopa, p. 483 



Mandibles without a palp Stenothoe, p. 484 



GG. Terminal uropods biramous; abdomen with the last three segments free. 



H. Anterior gnathopods with the carpus and propodus forming a chela LeucothoE, p. 486 



HH. Not as above. 



I. Carpus of the gnathopods joined in front of the proximal end of the propodus EusiRts, p. 493 



II. Carpus joined in the usual manner. 



J. Perceopods devoid of dactyls and peculiarly modified for digging Haustorius, p. 47(3 



.1.1. Pereopods with dactyls. 



K. First antenna? with an accessory fiagellum. 

 L. Terminal uropods flattened, projecting beyond the others. Gnathopods larger in the nude 

 than in the female, the second pair generally larger than the first; telson small, flattened, 

 cleft, or emarginate (Gammarid*). 

 M. Inner ramus of the terminal uropods scale-like, rudimentary; first antenna longer than 



the second Me lit a, p. 504 



MM. Inner ramus of terminal uropods not rudimentary, although often considerably smaller 

 than the outer. 

 N. Telson only slightly emarginate; thorax and abdomen dorsally 



carinated G ammarellis, p. 508 



NX. Telson deeply cleft. 

 O. Last three segments of the abdomen with fascicles of spines. 



First three abdominal segments produced behind into acute teeth.. Carinogammarus, p. 503 

 First three abdominal segments not so produced; abdomen not dorsally 



carinated Gammarus, p. 500 



