RHINOCARID^E. 



RHINOCARIS, n. g. (J. M. C). 

 Rhinocaris columbina, n. sp. 



PLATE XXXI, FIGS. 16-21. 



Cephalothorax elongate-siliquiform. Surface normally arched or sub-cylin- 

 drical, and probably somewhat flattened toward the ventral margin. The 

 anterior extremity is slightly depressed on the dorsum and produced into a 

 prora or rostrum, which is vertically flattened and gently deflected toward the 

 tip. On each side toward its base this prora bears a low ridge which is con- 

 tinued on the body of the carapace, accompanied by a faint ridge, which 

 lies in the axial line. These ridges appear to extend the entire length of the 

 carapace, though indistinctly seen on most examples on account of the lateral 

 compression which has usually fractured the carapace irregularly along the 

 dorsum. Below the prora the margin curves rapidly downward to the ventral 

 edge, where it is nearly straight for a short distance, thence curving upward 

 to the posterior margin, which is transverse and incurved over the axial 

 line, the posterior extremity being thus truncate. The optic spot appears to 

 be indicated by a faint tubercle in the cephalic region, close to the axial 

 line. There is no evidence of a nuchal furrow, and the limits of the cephalic 

 and thoracic areas are thus indistinguishable. 



Surface free of nodes or tubercles, but ornamented with faint pits on the 

 dorsal region and on the lateral areas with fine, raised, anastomosing lines, 

 which are sub-parallel to the margin, and converge toward the anterior and 

 posterior extremities. In all the specimens thus far obtained the carapace 



