Fresh-water Entomostraca of South America. 81 



small, shield-shaped, sub-erect, not forming any true rostrum. 

 No distinct shell-sculpture. Antennulæ and antennæ normal. 

 Lip-plate pyramidal in form. First pair of legs in female 

 with one of the apical spines unusually strong, almost un- 

 guiform, and denticulated at the edges. Exopodites of the 

 last 2 pairs rather large, laminar. Caudal part very slender 

 and narrow, sublinear, and provided with a lateral row of 

 very delicate denticles in addition to the marginal ones, 

 lower corner considerably produced, caudal claws slender and 

 almost straight; spermatic ducts in male opening at about 

 the middle of the ventral side of this part. 



Remarks. — This new genus somewhat resembles 

 the genus Alonopsis G. O. Sars, especially as regards the 

 structure of the caudal part; but in other respects it exhi- 

 bits well-marked differences. The carapace, for instance, is 

 far less compressed, and the valves are of a rather peculiar 

 appearance. Moreover, the structure of the legs seems to 

 exhibit several peculiarities. Besides the Brazilian species 

 described below, the Alonopsis orientalis of Daday unques- 

 tionably belongs to this genus. 



42. Euryalona occidentalis, n. sp. 



(PI. XII, figs. 1, a— h). 

 Specific Characters. — Female. Carapace 

 rather tumid, seen laterally, broadly quadrangular in outline, 

 height not quite equal to the length, dorsal margin evenly 

 arched, ventral somewhat irregularly flexuous, forming in 

 front of the middle an obtuse protuberance, from which it 

 ascends rather abruptly to the anterior margin, whereas be- 

 hind it runs more horizontally; posterior extremity but slightly 

 narrowed, and transversely truncated at the end, upper corner 



6 — Archiv for Math, og Naturv. B. XXIII. Nr. 3. 

 Trykt den 18. Marts 1901. 



