Fresh-water Entomostraca of South America. 43 



Fam. Lynceidse. 



Gen. Leydigiopsis, n. 



Generic Characters. — General form of body 

 resembling that in the genus Leydlgia, the carapace being 

 rather compressed and of broadly quadrangular form; cephalic 

 shield, however, produced in female to a long, more or less 

 recurved rostrum. Surface of shell without any distinct 

 sculpture; inferior edges of valves coarsely setiferous. Eye 

 comparatively small; ocellus equal to, or larger than the eye. 

 Antenuulæ short and thick, obliquely truncated at the tip. 

 Antennæ well developed, sometimes with the setæ excessively 

 elongated. Lamellar expansion of labrum triangular. Struc- 

 ture of legs about as in Leydigia; 1st pair in male termi- 

 nating in a strong procurved claw. Caudal part large, and 

 of same appearance in the two sexes, being more or less 

 expanded, lamellar, with a double row of strong marginal 

 spines, accompanied on each side by a lateral row of much 

 smaller, scale-like denticles. Intestine forming nearly a double 

 twist in the posterior part of the trunk. 



Remarks. — This new genus is somewhat inter- 

 mediate between Leydigia and Mona, resembling more the 

 former genus in general appearance and the structure of the 

 legs, while in some other anatomical details it seems to 

 come nearer to the latter. One characteristic feature of 

 the genus is the peculiar prolongation of the rostrum in 

 the female, recalling that in the genus Harporhynchus G. 

 O. Sars. I have had an opportunity of examining 2 distinct 

 species of this genus, to be described below. 



