MARINE GAMMARIDEAN AMPHIPODA 107 



Mandibular molar well developed, triturative, bearing ridges and teeth, 

 never extremely large or dominating mandible 7 



7. Peduncle of uropod 3 elongate, as long as or longer than rami of uropods 1-2 



(fig. 40) and more than twice as long as telson and peduncle of uropod 2, 

 uropod 3 also greatly exceeding apices of either uropods 1 or 2 and rami 

 elongate, subequal and nearly as long as rami of uropods 1-2 (uropod 3 is 

 usually missing on individuals of this category but melphidippids are also 

 recognized by the presence of dorsal teeth and serrations on the pleon, in 

 combination with short, subequal and evenly quadrate anterior coxae, 



plus strong hemispherical lateral ocular bulges on head) 8 ^ 



If peduncle of uropod 3 elongate as above then uropod 3 not strongly 

 exceeding apices of uropods 1-2; if peduncle of uropod 3 twice as long as 

 telson then uropod 3 not exceeding apices of uropods 1-2 or peduncle not 

 as long as rami of uropods 1-2; if uropod 3 greatly exceeding apices of 

 uropods 1-2 then inner ramus short and scale-like or peduncle not elongate 

 and not more than 1.2 times as long as peduncle of uropod 2, or rami much 

 shorter than peduncle; thus uropod 3 not like that of first part of this 

 couplet 9 



8. Coxae 2-3 longer than broad, pleon dorsally smooth, pereopod 5 very 



conspicuously longer than 3 or 4, head without lateral ocular bulges 

 (head often strongly rostrate) . . (exceptional) oedicerotidae (p. 373) 

 Coxae 2-3 very short and broader than long, pleon dorsally toothed and 

 serrate, pereopods 3-5 very long but subequal in length to each other, 

 head with strong hemispherical ocular bulges on sides. 



MELPHIDIPPIDAE (p. 368) 



Coxae 2-3 about as long as broad, pleonite 4 with one dorsal tooth, pereopods 

 3-5 long but subequal in length, head without lateral ocular bulges. 



Casco (Gammaridae) (p. 238) 



9. Coxae 1-3 successively and very distinctly shortened (fig. 43) , (and see mimic 



Megaluropus in Gammaridae and Casco with anteriorly acuminate coxa 



1 in Gammaridae) argissidae (p. 157) 



Coxae 2 or 3 always as long as or larger than coxa 1 10 



10. Telson entire, or emarginate, very short, coxa 4 not excavate posteriorly 



(pereopods often glandular) Section H 



Telson entire or cleft, short or long, coxa 4 usually excavate posteriorly or 

 acuminate (coxa 4 always excavate posteriorly or acuminate when telson 

 entire, but see Parapherusa in Section F and in Gammaridae), (pereopods 

 not glandular) 11 



11. Head massive (see definition in glossary), or with strongly down turned 



rostrum, or "shark-nose" rostral projection (fig. 31c), [gnathopods weak 



(fig. 31)] 12 



Head not massive or rostrum if present on massive head not downturned 

 (Hyperiopsidae have massive head, no rostrum; Pleustidae and some 

 Phoxocephalidae have downturned rostrum on small head) .... 13 



12. Pereopod 5 conspicuously longer than pereopods 3-4, at least 1.5 times as 



long as pereopod 4, accessory flagellum absent, or 1-articulate and short if 

 present, peduncle of uropod 3 always elongate and telson always half or less 

 as long as that peduncle and usually entire or rarely emarginate. 



OEDICEROTIDAE (p. 373) 



Pereopod 5 subequal to pereopod 4 in length, though both often elongate, 

 accessory flagellum always present and usually multiarticulate; when 1- 

 articulate, accessory flagellum elongate; peduncle of uropod 3 rarely 



2 See also the calliopiid Metaleptamphopus. 



285-135 O - 69 - 7 



