Fresh-water Entomostraca of South America. 89 



Gen. Camptocercus, Baird. 



Remarks. — Of this easily recognizable genus about 

 10 species have hitherto been described, all of which are 

 so nearly related, as to be distinguished only on a very close 

 examination. In by far the greater number of the species, 

 the infero-posteal corners of the valves are constantly armed 

 with a group of small serrations ; but in some few species 

 these serrations are wholly wanting. This, for instance, is 

 the case with the Australian form described by the present 

 author as C. australis, and also with the species recently 

 recorded by Dr. S. Ekman from Patagonia as C. aloniceps. 

 Another South American species, entirely without these ser- 

 rations, will be described below. 



45. Camptocercus similis, n. sp. 



(PI. XII, figs. 4, 4 a). 

 Specific Characters. — Female. Carapace, 

 as usual, greatly compressed and, seen laterally, of oblong 

 oval form, somewhat narrowed behind, dorsal margin gently 

 arched, ventral somewhat bulging in front and slightly con- 

 cave in the middle, posterior extremity obtusely rounded, 

 with the upper corner well marked. Head distinctly crested 

 along the middle, its dorsal edge evenly curved and con- 

 tinuous with that of the carapace, rostral projection apparently 

 transversely truncated at the tip, the edges of the fornix 

 terminating on each side in an angular corner and thus form- 

 ing a deep hollow, into which the antennulæ admit of being 

 received. Surface of shell sculptured with distinct but not 

 very densely crowded longitudinal striæ, which are partly 

 crossed in the anterior part of the valves by curved transverse 



