MARINE GAMMARIDEAN AMPHIPODA 



233 



place in Gammaridea Family Key A (p. 109). Its uropod 3 is even more 

 typically that of an ischyrocerid than is uropod 3 of Parapherusa. 



Another 13 genera of Gammaridae (in couplets 6-18) have vestigial 

 accessory flagella and cleft telsons and thus resemble Eusiridae. All 

 Eusiridae except Eusirogenes Stebbing have elongate telsons and that 

 genus is easily recognizable as a eusirid in its gnathopodal morphology. 

 Eusiridae also have slightly enlarged metasomal segments, the meta- 

 some having the length of 6 i)ereonal segments, whereas gammarids 

 have a metasome the length of only 5 pereonal segments. This is a 



Figure 95. — Gammaridae: a, Melita dentata (Krdyer) (Sars, 1895, pi. 181). Mouthparts 

 of Elasmopus rapax Costa (Sars, 1895, pi. 183): b, upper lip; c, lower lip; e, mandible; 

 f,g, maxillae 1, 2; h, maxilliped. Lower lip: d, Gammarellus honiari (Fabricius) (Sars, 

 1895, pi. 172). Gnathopod 2: f, Elasmopus ; j, Cheirocratus sundevalli (Rathke) (Sars, 

 1895, pi. 184). Gnathopod 1: k, Elasmopus; I, Cheirocratus. 



