73 



pleopoda; with the l,uiiiin-<>i>'nlu" in the presence of rudimentary exopodites to the 

 3rd and 4th pairs of legs in the female. From hoth these families it differs 

 conspicuously in the structure of the telson, and the uniarticulate inner ramus of 

 the uropoda. The marine forms of this family are very few in number, and 

 belong to two nearly-allied genera, to be described below. On the other hand, 

 as recently stated by the present author, this family is very abundantly repre- 

 sented in the Caspian Sea. exhibiting in this isolated basin quite a wonderful 

 variety of form. No less than 13 different species have hitherto been detected, 

 and some of these differ so widely in their external appearance from the marine 

 forms, that at first sight they might easily be supposed to belong to quite diffe- 

 rent families. A closer examination has proved, however, that they all agree in 

 the more essential anatomical features first pointed out in the genus Pseudocuma, 

 and for this reason they have all been described as members of this genus. If, 

 however, the establishment of the family Pseudocumidce be sanctioned, of course 

 a more general value must be ascribed to several of these characters ; and indeed 

 I am now of opinion that the Caspian species ought to be referred to several 

 distinct genera comprised within the present family, only one of them, P. cerca- 

 roidcs belonging to the type genus. The other species I propose to arrange 

 as follows: 



Gen. 1, Pterocuma, G. 0. Sars, with the species pectinata. SowinsJcyi and 

 rostrata: gen. 2, Stenocuma, G. 0. Sars, with the species gracilis, graciloides, 

 ft'iiuicauda and diastyloides : gen. 3, Schizorhynchus with the species bilamellatus, 

 > iitlorelloides, scabriusculus and abbreviatus; gen. 4, Caspiocuma with the species 

 campijlaspoides. 



Gen. 1. PseudOCUma, G. 0. Sars, 1864. 



Syn: Leucon, v. Beneden (not Kreyer). 



Generic Characters. Body not very slender, with the anterior division well 

 marked off from the posterior. Integuments thin, exhibiting a densely squamous 

 structure. Carapace of moderate size, dorsal face flattened and sloping in front, 

 lateral faces generally sculptured with oblique plicse, pseudorostral projection 

 more or less prominent, with the lateral parts contiguous along the dorsal line, 

 subrostral corners obtusangular. Exposed segments of trunk unarmed. Tail 



