On Fresh-water Entomostraca. 38 



somewhat in front of the middle. It is narrowly truncated 

 posteriorly, and strongly vaulted above, the dorsal margin 

 forming a bold and rather even curve until the tip of the 

 rostrum. The inferior edges of the valves are somewhat 

 protuberant in front of the middle, and join the anterior 

 edges by an abrupt curve; behind, they appear nearlv 

 straight, or very slightly convex in the middle, and ascend 

 obliquely to the infero-posteal corners, which are evenly 

 rounded off. The head is very procumbent, and, as in 

 the other species of the genus, to a certain degree mobile, 

 admitting of being bent in against the anterior part of the 

 valves. It terminates in a long and sharply-pointed rostrum, 

 which curves somewhat posteriorly, and projects considerably 

 beyond the free edges of the valves. The fornix appears 

 as an elevated sigmoid ridge, which joins the valves at a 

 very acute angle. 



The surface of the shell appears, in its greater part, 

 quite smooth, without any perceptible reticulation. In the 

 most anterior part of the valves, however, a very conspi- 

 cuous sculpturing is traced, consisting of from 10 to 12 

 curved, transverse striæ, which run parallel to the ante- 

 rior edges, and are very sharply marked. The inferior 

 edges of the valves are throughout fringed with delicate 

 bristles, which, especially in their posterior part, are rather 

 conspicuous and finely ciliated. The infero-posteal corners 

 are quite smooth, without the slightest trace of the strong 

 denticles occurring here in other species. 



The eye is of moderate size, and occupies its usual place. 



The ocellus is scarcely half as large, and occurs much 

 nearer to the eye than to the tip of the rostrum. 



The antennulæ are short and thick, extending scarcely 

 beyond the middle of the rostrum. 



