forms anteriorly a very prominent curve, giving to the head the 

 appearance of being obliquely truncate in front. Posteriorly, 

 the inferior margin of the head terminates with a very slight 

 triangular prominence, on either side of which the antennulae 

 are seen to project; anteriorly, it joins the dorsal edge by a very 

 sharp curve. The latter edge is slightly convex and not defined 

 from the dorsal edge of the carapace by any intervening im- 

 pression or sinus, both forming together a quite uninterrupted 

 even curve. 



The carapace, or shell, is obliquely oblong in form and, as 

 in most other Cladocera, forms inferiorly two movable flaps or 

 valves, protecting the branchial legs, though more or less widely 

 separate inferiorly and posteriorly (see fig. 2). These valves are 

 comparatively narrow and do not cover the oral parts at the 

 sides, nor are the latter organs, as in Latona, protected above 

 by any distinct fornicate plates, interposed laterally between the 

 head and the carapace. The inferior edges of the valves are 

 throughout the greater part of their length well-nigh straight. 

 Anteriorly, they ascend by an even curve, forming in front a 

 rounded flap, to the inner side of which several strong muscular 

 bundles, originating from the sides of the body immediately be- 

 hind the oral parts, are seen to affix themselves. By the aid of 

 these muscles the valves are moved to a certain extent, being 

 by their contraction approached to each other. Posteriorly, the 

 inferior edges of the valves unite the posterior, by a rather 

 prominent curve; the latter are somewhat oblique, though less 

 so than in Latona, and terminate above with a slightly pro- 

 jecting obtuse angle. The dorsal edge of the carapace exhibits a 

 more or less projecting curve in the middle, according to the number 

 of eggs or embryos contained within the dorsal cavity of the shell or 

 matrix. As seen in a dorsal or ventral aspect (fig. 2) the body 

 is somewhat fusiform, the greatest breadth being about in the 

 middle, whence the body successively tapers to either extremity, 

 though somewhat more abruptly in front, the head appearing 

 obtusely conical in form. 



The free edges of the valves are fringed, as in Latona 



