26 



G. 0. SARS. 



[No. 8. 



aquaries, and thus preventing the full development of any feebler 

 species. 



3. Ceriodaphnia cornuta, n. sp. 



(Pl. 5, figs. 1—3). 



Specific Character. — Female: — Head muen depressed, 

 with frontal part slightly dilated, and jutting out as two acute pro- 

 cesses, the on constituting a kind of rostrum, the other a corni- 

 form projection of the front. Carapace broadly oval, and rather 

 tumid, jutting out posteriorly as a short bifurcate prolation. 

 Whole of shell distinctly reticulate, with comparatively large, 

 polygonal meshes; free edges of valves smooth. Eye of moder- 

 ate size, ocular spot exceedingly small. Antennulæ rather short, 

 fusiform, tentacular seta affixed about in the middle. Antennæ 

 comparatively feeble in structure. Tail provided with 2 distinct 

 dorsal processes, posterior very broad, and having at hinder 

 part a fascicle of fine hairs, terminal section evenly tapered, 

 with dorsal margin well-nigh straight, and exhibiting about 8 

 pairs of rather small denticles; apical claws without secondary 

 teeth at base. Body pellucid, with but a faint greenish tinge. 

 Length of ovigerous female 0,60 mm. 



Re marks. — This form may be easily distinguished from 

 all hitherto known species by the two peculiar projections of the 

 frontal part, the anterior of which has the appearance of a small, 

 anteriorly directed cornicle : hence the specific denomination. The 

 C. textilis of Dana would appear to exhibit a similar rostral pro- 

 jection, but wants every trace of the characteristic frontal cor- 

 nicle. Of our Northern forms, C. quadrangula Muller, is that 

 most nearly related to the present species. 



Description of the Female. — The specimen examined 

 measures in length 0,60 mm only, and thus ranks among the 

 smaller species of the genus. 



The general form of the body (see Pl. 5, fig. 1) appears, as 

 in the other species, rather short and thickset, also somewhat 

 tumid, though the breadth does not fully equal the height. 



The head is very much depressed, and marked off from the 



