Fresh-water Entomostraca of South America. 23 



7. Simoceplialus semiserratus, n. sp. 



(PL IV, figs. 1-9). 

 Specific Characters. — Female. Carapace, 

 seen laterally, broadly oval or somewhat rhomboid in out- 

 line, slightly widening behind, dorsal margin evenly arched, 

 ventral, as usual, bulging in front, and joining the hind edges 

 at an obtuse angle, these being oblique and almost straight ; 

 posterior prominence very slight, and located above the axis 

 of the body. Head of moderate size, and defined above 

 from the carapace by a rather conspicuous depression, dorsal 

 margin somewhat arched in its posterior part, front distinctly 

 angular, and armed just above the angle with 3 extremely 

 small denticles, ventral margin straight and somewhat as- 

 cending, rostral projection very small; fornix normally 

 developed, though somewhat less prominent than in the 

 succeeding species. Surface of shell exhibiting the usual 

 oblique striation, posterior part of dorsal margin distinctly 

 denticulate, the denticles being also continued for a short 

 distance along the hind edges, immediately below the pos- 

 terior prominence, the remainder of these edges being, how- 

 ever, quite smooth, though exhibiting inside the margin the 

 usual series of delicate spinules. Eye of moderate size; 

 ocellus small, subfusiform. Caudal part moderately broad, 

 supra-anal prominence somewhat projecting and finely denti- 

 culate, anal denticles about 13 on each side, caudal claws 

 finely denticulated throughout their whole length. M a 1 e, as 

 usual, very much smaller than female, and having the 

 carapace narrower, with the posterior prominence almost 

 obsolete. Antennulæ and 1st pair of legs transformed in 

 the usual manner. Caudal part much narrower than in 

 female, and with only 3 anal denticles on each side. Colour 



