GAMMARIDEAN AMPHIPODA 89 



(1962a) segregated Uristes and ''''Ti^yphosa''' on the relative lengths of 

 articles 5 and 6 of gnathopod 1. This resulted in an unnatural mix- 

 ture of species with strongly and weakly developed prebuccal com- 

 plexes and species with large or small heads. The ordinary species 

 of ''^Ti'yphosa''' has a large head and a w^ell-developed prebuccal com- 

 plex with the epistome dominatmg the upper lip ; presumably the type- 

 species of Uristes has a small head and small prebuccal complex with 

 neither the epistome nor the upper lip dominating; the cephalic size 

 of the type-species of Amhasiopsis is not described and the prebuccal 

 complex is small, with the upper lip slightly dominatmg the epistome. 

 All European tryphosas have a characteristically tapermg coxa 1, the 

 type of Uristes has a slightly tapering coxa 1 and the type of Am- 

 hasiopsis has a strongly tapering, shortened, acute coxa 1. But coxa 1 

 is intergraded by various species. '^ Uristes^'' antennibrevls J. L. Barn- 

 ard (1962a) stands between Ambaslopsls and the other two genera 

 and Uristes harhatipes (Stebbing, 1888) intergrades ^"I'ryphosa''' and 

 Uristes. On the other hand, Uristes {^%=Pseudotryphosa) uiiibonata 

 Sars (1895) has an even more reduced coxa 1 than most tryphosas and 

 much more than that of the type-species of Uristes. 



The relative sizes of heads are difficult to measure; they are not 

 easily related to sizes of coxae or even segments because these also 

 vary from species to species. Nevertheless, the mouthpart groups of 

 Uristes (usmg only the type-species and U. urnbo7iatus as examples) 

 are so reduced in size that they are hidden by the coxae, whereas in 

 '■'■Tryphosa''' the mouthpart bundle is large and projects well below the 

 anterior coxae. Few species of Uristes or '"''Trypliosa''' outside of Eu- 

 rope or those erected by Stebbing have been sufficiently well described 

 to permit an analysis of the variability of this character. The mouth- 

 parts of Uristes antennlbrevis seem to be intermediate between those 

 of ''''TryplioscC and Uristes.^ although the head is relatively large. 

 Uristes typhlops (Sars, 1879) has a small head bearing strongly pro- 

 jecting mouthparts. Sars showed coxa 1 to be expanded, but J. L. 

 Barnard (1962a) described a subspecies with the typical coxa 1. The 

 tjrpe and other European tryphosas have a characteristically concave 

 anterior edge on coxa 1, whereas the type of Uristes and U. wnbonatus 

 have a slightly convex anterior edge. The generic value of this 

 character is doubtful, however, because rearrangement of the known 

 species on this basis would again throw together large- and small- 

 headed species with those having large and small mouthpart clusters. 

 For example, U. antennibrevls has a large head but a convex first 

 coxal margin and U. typhlops mediator J. L. Barnard has a small head, 

 small buccal mass and a convex coxal margin. 



The significance of first coxal shapes as generic characters is qucs- 



