﻿CAMAROPHORA. 



71 



Spec. Char. Sub-pentagonal, rather depressed ; almost circular, transverse, or slightly 

 elongated ; surface smooth, dorsal valve rather deeper and more convex than the opposite 

 one, with a mesial fold of moderate elevation, which, commencing at about the middle of 

 the shell, extends to the front. This fold is either entirely smooth and evenly rounded, or 

 divided near the front into two or three small ribs. The lateral portions of the valves are 

 smooth, and usually without any rib. Dorsal valve moderately convex, the sinus being 

 either entirely smooth or divided close to the front by one or two small ribs : beak small, 

 incurved. Proportions variable : two specimens measured — 

 Length 7^, width 7^, depth 5 lines. 

 6 „ 7 „ 4 „ 



Obs. I have not been able to examine the interior of this shell, but the single median 

 line, which can be observed through the transparency of the shell, and which extends for 

 a short distance along the back of the beak, leaves no doubt as to this species being a 

 Camarophoria. It is the same as described and figured by Phillips under the designation 

 of Terebratula rhomboidea, at p. 88 of his ' Pala30zoic Fossils of Cornwall, Devon, &c./ 

 and this distinguished palaeontologist is quite correct, I think, in stating that there 

 appears no important difference between this Devonian shell and that so-named Yorkshire 

 Carboniferous species. 



In his ' Geology of Yorkshire,' Phillips's Terebratula rhomboidea is described as having 

 no lateral plaits ; and although this observation is correct for the greater number of speci- 

 mens, it is not so for other examples, which possess two or three small ribs close to the 

 margin on the lateral portions of the shell, as may be seen in one of Phillips's own 

 typical examples, and in this last condition exactly resembles Camarophoria globulina of 

 Schlotheim. 



The Permian shell, it is true, does not attain (so far as my knowledge goes) a third 

 of the size of the largest Carboniferous specimens, or a fourth or fifth of the Devonian 

 examples ; still, I cannot divest from my mind the intimate relationship which seems to 

 exist between the shells in question from the three formations, and it appears to me 

 probable or possible that the small Permian C. globulina is merely a small race derived 

 in natural succession from the Devonian and Carboniferous species, which has been de- 

 scribed by Phillips under the denomination of " rhomboidea!' It is also true that in 

 the Permian C. globulina one or two small angular ribs are usually present near the 

 margin on each of the lateral portions of the valve, while in general the lateral portions of 

 the valves remain smooth and without ribs in the Devonian and Carboniferous types ; 

 but there are likewise specimens of the Permian shell which are similarly constructed, 

 and it is therefore evident that neither the presence nor absence of these lateral ribs can 

 be brought forward as an essential character of the species. However, as I may after all 

 be mistaken in my judgment in this matter, and in consideration of the much larger 

 dimensions of the Devonian shell, as well as of its exact similarity to Phillips's Carboni- 

 ferous specimens, which do not show any lateral ribs, it may be best to retain (pro- 



