318 PALEONTOLOGY OF OHIO. 



view of obtaining his opinion respecting their relations to the genus 

 Ceratiocaris, and he informed me that Dr. S. I. Smith, of that city, and 

 himself concur in the opinion that they do not properly belong to the 

 same genus as the typical forms of Ceratiocaris. 



The differences to which I allude consist first in the general form of 

 the carapace valves, which, instead of being truncated with a nearly 

 straight outline from below forward and upward, are truncated backward 

 and upward, with a profoundly sinuous outline, the sinus being directed 

 somewhat obliquely forward and upward, -^hile the posterior extremity 

 of the dorsal margin is produced, pointed, and curved downward. Again, 

 they show a peculiar inflection of the ventral margin, which gives it a 

 more or less carinate appearance. In the species C. Bradleyi, this mar- 

 gin is always fixed along this line at an acute angle inward and upward, 

 while in the species C. elytroides it is less strongly inflected, though the 

 linear carina is well defined, and sometimes minutely crenated. This 

 last mentioned species also shows another linear, minutely crenate carina 

 or ridge near the dorsal margin, and would, therefore, bear some resem- 

 blance to Dithyrocaris in this respect, but otherwise, particularly in the 

 form of its carapace valves, it is quite distinct from that type. 



It is also worthy of note that none of the specimens yet obtained show 

 any traces of an ocular tubercle or spot, so constantly seen in the typi- 

 cal species of Ceratiocaris. Again, they always present a clear, smooth 

 outline to the dorsal margin of the carapace valves, thus indicating that 

 they were merely connected there by a kind of flexible ligament, while 

 the valves of Ceratiocaris were supposed by Prof. McCoy to be anchylosed, 

 and rigidly united at a fixed angle along the dorsal margin. 



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

 all, of these difierences, but from deference to the general reluctance of 

 geologists and some palaeontologists to accept new genera separated under 

 such circumstances, I merely proposed, in first describing the following 

 species, to arrange them provisionally as a subgenus of Ceratiocaris, under 

 the^name Colpocaris, in allusion to the sinus of the posterior margin. 

 The same arrangement is also continued, provisionally, here. 



Ceratiocaris (Colpocaris) Bradleyi, Meek. 



Plate 18, figs. 6a, b, c, d, e. 



Ceratiocaris (Colpocaris) Bradleyi, Meek {1872) ; Proceed. Acad. Nat Sci., Philad., 

 XXIV, 332. 



Carapace valves large, rhombic-subelliptic, more than twice as long as 

 high, moderately convex ; dorsal margin forming a broad, depressed arch 

 from end to end; ventral margin more deeply arched downward than 



