332 PROCEEDINGS OF THE ACADEMY OF 



described along with Oliio fossils, and will be described and illus- 

 trated in the report of the geological survey of that State. 



CEEATIOCAEIS (COLPOCARIS) BRADLEYI, Meek. 



Carapace-valves rhombic-subclliptic, more than twice as long as 

 high, moderately convex; dorsal margins forming a very broad 

 depressed arch from end to end, ventral margin more deeply 

 arched, the most prominent part being near the middle, along 

 which it is abruptly inflected, while its entire length, owing to 

 the obliquity of the posterior end, is shorter than the dorsal 

 margin ; posterior deeply and obliquely sinuous, so as to cause 

 the posterior extremity of the dorsal margin to terminate in an 

 acute, downward curved projection, that extends decidedly farther 

 back tlian the more obtuse termination of the lower margin; an- 

 terior end narrowed, with its margin rounded up from below, so 

 as to connect with the dorsal nearly at right angles above. Sur- 

 face smooth, but showing, under amaguifier, very minute reticulated 

 markings. Ocular spots wanting. 



Length, about 2.75 inches; height, about 1.25 inch. 



This species agrees most nearly in size and form with Ceratio- 

 caris ? sinuatun, Meek and Worthen, from the lower coal-measures 

 of Grundy County, Illinois; and was found b}^ Prof Bradley, 

 enveloped in exactly the same way, in concretions. It differs, 

 however, in being proportionally narrower in its vertical diameter, 

 with the most prominent part of its basal margin more nearly 

 central. The posterior extremity of its dorsal naargiu also differs 

 in being more produced and more pointed, as well as more curved 

 downward ; while that of its lower margin is proportionally 

 shorter, owing to the obliquity of the deep sinus of the posterior 

 end of the valves. The C? si7iuatus, however, belongs evidently 

 to the same group. 



On first examining this and the following species, I was at once 

 impressed with the general resemblance of the specimens to the 

 genus Ceratiocaris of McCoy. On carefully comparing them, 

 however, with the original typical species of that genus, such as G. 

 solenoides, G. ellipticus, and the more recently described G.ornatus 

 of McCoy, from the Silurian, I observed certain diilerences that 

 led me to doubt the propriety of referring our species to the same 

 group. Consequently, I sent some of the specimens to Prof. 

 Dana, of New Haven, for examination, and he writes that both 



[xAIarch 19, 



