1885.] 



CLADOCERA. 



19 



orly. front obtusely rounded, rostrum wanting. Carapace oblong, 

 with ventral margins incurved and densely hispid, antero-lateral 

 corners projecting. Spine of carapace comparatively short. An- 

 tennulæ greatly produced, with peduncle and flagellum uniform 

 in length. Tail without any dorsal process, anal margin slightly 

 incurved and with very few denticles. 



Body in both sexes rather pellucid, having merely a faint 

 greenish tinge. Length of female (including spine) reaching 

 3,90 mm, of male 1,60 mm. 



Re marks. — This would seem to be the most striking 

 form among the Cladocera raised from the mud, and may easily 

 be distinguished from all other known Daphniæ by the prodig- 

 iously developed lanceolate prolongation of the head, the peculiar 

 shape of the fornix, the distinct dorsal impression between head 

 and carapace, and the remarkably long and distant marginal den- 

 ticles of the val ves. Moreover, as shown above, the ephippium 

 differs somewhat in form from that in most other Daphniæ. 



Description of the Female. — The total length of the 

 largest specimens examined was 3,90 mm, the spine of the cara- 

 pace measuring 1.65 mm; hence the species somewhat exceeds 

 in size the larger form of our common D. longispina, Muller. 



The general form of the body (see Pl. 3, figs. 1, 2) is some- 

 what compressed, the (greatest breadth scarcely exceeding half 

 the height. 



- ^.The head, unlike what occurs in the known species of this 

 genus, is well defined from the carapace by a distinct dorsal 

 impression. In a lateral aspect (see fig. 1), it exhibits a some- 

 what triangular form, the top of the triangle being drawn out to 

 a very large spear-shaped prolation, pointing a trifle downward. 

 The dorsal margin of the head is gently arched posteriorly, 

 whereas it anteriorly becomes almost straight, adjoining without 

 any interruption the upper edge of the frontal prolation. The 

 ventral margin of the head, on the other hand, forms, along with 

 the lower edge of the prolation, a distinct sinus, and is very 

 slightly arched, running out posteriorly as an acute-angled pro- 

 jection — the so-called rostrum. The fornix occurs very prominent 



2* 



