NATURAL SCIENCES OF PHILADELPHIA. 333 



Dr. S. I. Smith, of that city, and himself, concur in the opinion 

 that they do not properlj- belong to the same genus as the typical 

 forms of Ceratiocaris. 



The differences to which I have alluded consist, first, in the 

 form of the carapace-valves, which, instead of being truncated, with 

 a uearl}^ straight outline from below forward and upward, are 

 truncated from above forward and downward, with a j)rofoundly 

 sinuous outline, the sinus being directed forward and upAvard, 

 while the posterior extremity of the dorsal margin is produced, 

 pointed, and curved downward. Again, they show a peculiar 

 flexure of the ventral margin, so as to form a kind of linear 

 carina. In the species Bt^adleyi, this margin is always inflected 

 along this line, at an acute angle inward and upward ; while in 

 the species elytroides, it is less strongly deflected, though the 

 linear carina is equally well defined, and sometimes minutely 

 crenated. This species also shows another minutely crenated, 

 obscurely defined carina below the dorsal margin, and would 

 therefore bear some resemblance to Dithyrocaris, in this respects 

 but otherwise, particularl}' in form, its carapace-valves are quite 

 different from those of that type. 



It is also worthy of note, that none of the several specimens 

 of these species show any traces of the ocular spot or tubercle, 

 constantly seen in the typical species of Ceratiocaris; and that 

 the}^ show a clean, smooth outline to the dorsal mai'gins of the 

 carapace-valves, indicating that they were only united hy a mem- 

 brane ; while those of Ceratiocaris were supposed by Prof. 

 McCoy to be anchylosed, and rigidly united at a fixed angle 

 along the dorsal margin. 



I have no doubt in regard to the importance of some, if not all, 

 of these points of difterence, but, knowing how slow many geolo- 

 gists (who are generally far behind zoologists in the discrimination 

 of genera) are to accept such divisions, I have merely distinguished 

 these species for the present, as belonging to a subgenus of Cera- 

 tiocaris, under the name ColpocaiHs, in allusion to the sinus of 

 the posterior margin. 



Locality and position. — Base of the Waverley group, at Dan- 

 ville, Kentucky. Prof. Bradley's collection. 



18T2.] 



