382 



NORTH AMERICAN INDEX FOSSILS. 



XII. Rhinocaris Clarke. 



Valves in contact at only a single point; divided by median 

 dorsal plate and anterior rostrum ; carapace smooth, except for 

 fine, raised longitudinal striae; ocular nodes well defined; posterior 

 margin concave ; abdomen with two or three segments, the last 

 one the longest, all diagonally striated ; telson broad ; cercopods 

 fimbriated on their margins. Devonic. 



23. R. columbina Clarke. Devonic. 

 Rostrum long and slender ; median plate spatulate ; broadening 



furrows diverge backwards from the eyes ; lateral carinae very faint. 

 Hamilton group of New York. 



24. R. scaphoptera Clarke. (Fig. 1688, a and J.) Devonic. 

 More pointed anteriorly than preceding; rostrum strongly 



curved, rather thick; valves with posterior ventral spinous pro- 



FlG. 1688. a, d, Rhinocaris scaphoptei-a, exterior of left valve and both valves con- 

 joined, the latter X 2 ; b, c (cen'er) R. capsella, left and right views of two folded 

 carapaces, the first X 2. (After Clarke.) 



longation and strong lateral carina; surface with elevated lines 

 parallel to ventral margin, stronger and more frequently inter- 

 rupted than in R. columbina. 



Hamilton and Ithaca beds of New York. 



25. R. capsella Hall and Clarke. (Fig. 1688, &, c.) Devonic. 



Carapace rounded posteriorly; with a few faint ridges near 

 anterobasal margin; longitudinal striae well marked; no spine on 

 posterior margin. 



Hamilton and Ithaca shales of New York. 



