MARESTE GAMMARIDEAN AMPHIPODA 261 



Hyalellidae and Hyalidae 



[see Superfamily Taiitroidea] 



Hyperiopsidae 



Figures 101, 102 



Diagnosis. — Accessory flagellum well developed; article 4 of 

 pereopods 1-2 greatly elongate ; palp of first maxilla claviform, slightly 

 geniculate; gnathopods feeble, simple. See Vitjazianidae, Astyridae, 

 Stilipedidae, Synopiidae. 



Description. — Accessory flagellum well developed, its articles 

 very elongate; body variable, smooth or carinate, head globular 

 (resembling hyperiids), subglobular or nearly normal, but rarely 

 bearing distinct lateral lobes; coxae variable, first four small and 

 uniform or coxa 4 enlarged and covering anterior coxae; upper lip 

 with minute incision; mandibular body very short, poorly toothed, 

 molar very small, weakly triturative or not, palp immense; lower lip 

 without inner lobes, outer lobes often alate; palp of maxilla 1 biartic- 

 ulate, article 2 slightly or greatly bent medially (at least on one side) ; 

 maxilla 2 and maxilliped normal; gnathopods feeble or nearly simple; 

 uropod 3 biramous; telson cleft or entire, ^^ith apical ornamentation. 



It is difficult, at first glance, to justify a familial association of the 

 two hyperiopsid genera. Hyperiopsis resembles an hyperiid amphipod. 

 It has a globular head, smooth body and short uniform coxae. Parar- 

 gissa has the normal appearance of a gammaridean and although the 

 head is subglobular it is rather small and may have lateral lobes; its 

 fourth coxa is enlarged and covers the smaller coxae 1-3. Nevertheless, 

 Hyperiopsis and Parargissa share some features that are unusual in 

 the Gammaridea: (1) the peculiar first maxillary palps of which the 

 second articles are claviform and slightly bent on at least one of the 

 maxillae; (2) the very short body of the mandible with a nearly 

 untoothed cutting edge and a very small, poorly developed molar; (3) 

 the great elongation of article 4 on pereopods 1 and 2, a condition 

 rarely occurring in other families (cf. Ampeliscidae) ; (4) the elonga- 

 tion of article 1 of the first antennal fiagellum (not uncommon in some 

 other families, viz. Lysianassidae, Synopiidae). 



Relationship. — The combination of the elongate article 4 of pere- 

 opods 1 and 2 with the bent first maxillary palp separates this family 

 from the following similar families: Astyridae, Synopiidae, Pardalis- 

 cidae, and Vitjazianidae. 



The Ampeliscidae resemble hyperiopsids because of the elongate 

 fourth articles of pereopods 1-2, but ampeliscids lack accessory 

 flagella and have well-developed mandibular molars. 



