188 REPORT ON THE STATE CABINET. 



The Atrupa aspera^ or its representative, in the beds at Independence 

 and Waverly, has the dorsal valve very gibbous, with the ventral valve 

 nearly flat or concave towards the margins. In the higher beds at Rock- 

 ford there is a form, in which the valves are more nearly equal in 

 convexity, the plications fewer, and the shell has the aspect and character 

 of A. hystrix of the Chemung group in New York. We are able, there- 

 fore, in the rocks of this age, to recognize over a wide area four varieties 

 of form and surface marking which are pretty constant, two of which 

 may be referred to the type of ^4. asptera and two to that of A. reticularis. 



A single species of Coelospira occurs in the Corniferous limestone, 

 which, so far as known, possesses no characters differing from Coelospira 

 concava of the Lower Helderberg group. 



With this genus are concluded all the genera bearing calcified spires : 

 these appendages, though probably possessed by some of the following 

 genera, were doubtless fleshy or cartilaginous organs, and have not been 

 preserved. 



Under the Family RHYNCHONELLiDJi:, the species usually referred to the 

 Genus Rhynchonella are shown to differ from recent species referred to 

 that genus ; while at the same time the internal structure and appendages 

 of the typical species of the genus (i?. loxia) remain unknown or unillus- 

 trated. Under these circumstances, the name Stenocisma, proposed by 

 Mr. Conrad in 1841, is revived, and applied to most of the rhynchonelloid 

 forms of the rocks under consideration. Since, however, Rynchonella 

 has come to be so well known, and many of the species have been 

 described under the generic designation, the name is still retained. The 

 following species are recognized in the Carboniferous limestone : 



Rhynchonella [Stenocisma) tethys, 



R. 8. bilUngsi (in place of R. thalia of Billings ; 



name preoccupied); 

 R. S. Carolina (n. s.), 



RJ 8.9 royana (n. s.). 



In the Hamilton group, we have : 



Rhynchonella {^Stenocisma) hor.sfordi, 

 R. 8. sappho, 



R. 8. congregata, 



R. 8. prolip'ca (n. s.), 



R. 8. dotis (ii. s.), 



R. 8. carica (n. s.). 



