FOSSILS OF THE CARBONIFEROUS LIMESTONES. 295 



beak is gently incurved, and exhibits a small circular foramen under 

 its angular extremity. Length five lines, width five lines, depth three 

 lines. 



Fig. 94. — Ehyvchonella Acadiensis, Davidson ; iiat. size and magnified. 



" Of this shell I have seen but two specimens, which I detached from 

 a lump of the Brookfield shell-limestone, and of which one exhibited 

 the two curved internal lamellae characteristic of the genus Rhijnchonclla. 

 It is quite distinct from young shells of Rhynchonella pugniis and R. 

 pleurodon. In the last-named species the ribs that adorn the lateral 

 portions of the dorsal valve are very much curved, while those of the 

 ventral are nearly straight, with their extremities bent upwards ; in 

 addition to which, the ribs begin to be longitudinally grooved along 

 their median portion at some distance from the margin. None of 

 these characters are observable in the small Rhynchonella under 

 description. 



" Rhynchonella, sp. — Upon some fragments of Lower Carboniferous 

 limestone brought from Nova Scotia by Sir C. Lyell are several imper- 

 fect, undeterminable valves of a Rhynchonella, which differs from the 

 preceding species by its size, as well as by the number of its small 

 radiating ribs. Of these last I have counted as many as thirty-five 

 or forty upon each valve. In size it appears to have measured about 

 seven or eight lines in length by nine in width. I abstain from 

 proposing for it a specific denomination, as the material is so imper- 

 fect. The specimen belongs to the Geological Society. 



'■'•Rhynchonella piignus {J), Martin, sp., Petrif. Derb., tab. 22, figs. 

 4, 5, 1809. 



" Two or three very small specimens, received from Dr Dawson after 

 my plate had been completed, much resemble certain young shells of 

 Martin's species ; they arc derived from the Lower Carboniferous 

 limestone of Windsor and East River. 



"■ Strophomena analor/a, T^hillips (Fig. 95). 



" Producta analoga, I'hillips, Gcol. Yorksh., vol. ii. pi. 7, fig. 10, 

 1836. 



" Upon a specimen of dark, impure limestone brought from Nova 



