170 U.S. NATIONAL MUSEUM BULLETEST 271 



because they are almost perfect intergrades between the lower lips 

 of pleustids and calliopiids. 



Calliopiids (and pleustids) may be confused with isaeids, ischyroce- 

 rids, and ampithoids unless one notes the absence of pereopodal glands 

 in Calliopiidae. The isaeid-like families have a fleshy telson which is 

 usually much shorter than broad, and generally have imexcavate 

 posterior margins on the fourth coxae. 



The Laphystiopsidae, very closely related to the Calliopiidae, 

 differ primarily by the poorly developed mandibular molar. One 

 laphystiopsid genus, Prolaphystius, however is included in the key 

 to the Calliopiidae because of its uncertain position in the Laphystiop- 

 sidae. It has a moderately well developed molar. 



The Vitjazianidae are distinguished by their distinctly simple 

 first gnathopods. Pleustidae have their characteristic lower lips. 



The Paramphithoidae are characterized by cuspidate or pointed 

 anterior coxae. Occasionally these acuminations are extremely weak 

 and coxae 1-4 are scarcely excavate ventrally. 



One calliopiid, Halirages regis (Stebbing, 1914) i=H. stebbingi 

 Schellenberg, 1931; =H. huxleyanus Stebbing, not Bate, 1862) has 

 subacuminate anterior coxae and thus keys to Paramphithoe, type- 

 genus of Paramphithoidae. Halirages regis has strongly developed 

 gnathopods with ovate sixth articles and thus differs from most of its 

 congeners and Paramphithoe. Superficially, this species forms the 

 perfect intergrade between Calliopiidae and Paramphithoidae and 

 distinctions between the two families are completely confounded; 

 further study of the problem is warranted. Some species of Cleippides 

 also have subacuminate coxae. 



Soine genera of the Gammaridae, such as Falklandella, might be 

 placed in the Calliopiidae, except that Falklandella has short rami 

 of uropod 3, not characteristic of Calliopiidae. Gammarellus and 

 Weyprechtia with entire telson, and Parapherusa are not assignable to 

 Calliopiidae because of their multiarticulate accessory flagella. 



The Oedicerotidae have disproportionately long fifth pereopods and 

 densely setose coxae and pereopods. 



Most synopiids have a multiarticulate accessory flagellum but 

 a few have an accessory flagellum similar to that of eusirids. The 

 massive head of synopiids is characteristic, especially because of its 

 strongly deflexed rostrum. Synopiid gnathopods are feeble, whereas 

 those of eusirids are usually powerful. 



Gnathopods within a genus are highly variable as to proportions 

 of articles 5 and 6; departures from a "normal theme" are seen 

 in Oradarea and Leptamphopus , which have exceptionally elongate 

 sixth articles of gnathopod 2. Cleippides has a relatively elongate 

 second gnathopod. Harpinioides has peculiar, bent sixth articles. 



