11 



of all the three epimerons or only the last epimeron is drawn into a small 

 denticle. In hyperiideans strong denticles, spines, and processes on the 

 epimerons never develop, which are so characteristic of gammarideans. 

 The last three abdominal somites form the urosoma, bearing three pairs 

 of biramous appendages — the uropods. Urosomites II and III are fused, 

 although in some Physosomata a suture can be seen between them. 



Normally, all the three pairs of uropods are biramous, with free 

 endo-and exopodites which, however, are never two-segmented. In some 

 groups, in one or all the uropods, the endopodite is fused with the 

 basipodite and the exopodite is reduced (Cystisoma, Oxycephalus, Lepto- 

 cotis, Simorhynchotus, Tullbergella), sometimes to a small spine (Scina, 

 Spinoscina, Rhabdosoma), or totally absent (uropod I in Ctenoscina). 

 20 Sometimes, contrarily, the basipodite and one of the rami are reduced, 

 in which case the uropods acquire the shape of an oval plate (family 

 Phrosinidae). In some groups there is a tendency toward decrease in size 

 and reduction of uropods II (Phronima, Rhabdosoma) down to modi- 

 fication into a small spine (females of Phronimella) and even to total 

 absence (Cystisoma). 



The entire and unarmed telson is usually shorter or longer than 

 the basipodite of uropods III; usually it is free but sometimes fused 

 with urosomite III (Oxycephalidae except Rhabdosoma, Platyscelidae, 

 Parascelidae, Pseudolycaea). 



The internal structure of amphipods has been discussed by E.F. 

 Gur'yanova (1951), so we shall not dwell on it here. 



2. NOTES ON THE TAXONOMY AND PHYLOGENY OF THE 



SUBORDER 



Significant morphological differences within the suborder hyperiidea 

 make it possible to divide it into several, more or less independent groups, 

 each comprising many families. 



Woltereck proposed the division of the suborder into two tribes.' 



1 . Hyperiidea Gammaridea — animals with a gammaridean body 

 shape, short small head, and small eyes, which may even be totally 

 absent, and free coxal plates. Depending on whether the inner lobes of 

 the maxillipeds are fused or separated, Woltereck divides the tribe into two 

 subtribes: Primitiva and Derivata. Those families of the Primitiva whose 

 members retained the mandibular palp, were included by him under the 

 group Completa, and those that lost the palp under the group Incompleta. 



2. Hyperiidea Genuina — forms with a large, inflated head, with eyes 

 occupying a large part of the head, in which the coxal plates may be fused 



' In the current nomenclature, the tribes as interpreted by Woltereck and subsequent 

 authors correspond to infraorders (Bowman and Gruner, 1973). 



