246 PERMIAN FOSSILS. 



Magasidce, p. 142., 



Mr. Davidson has lately described a new genus under the name of Waltonia, and placed it, correctly I 

 think, in the present family. I formerly had some doubts as to the distinctiveness of Magasidce ; but I 

 now think, that it is essentially different from both Terebratulidce and TerehratellidcB, in its apophysary 

 system being without the recurved portion : in having a doubly-attached loop, it appears to be more related 

 to the last-named family than to the first one. 



Terebratula, p. 143. 



Mr. J. G. Jeffreys having kindly favoured me with some instructive specimens of Terebratulina caput- 

 serpentis, with the loop and labial appendages preserved, and Mr. Davidson having sent me a sketch of the 

 apophysis of Terebratula vitrea, I am now better enabled to appreciate the reasons which led M. d'Orbigny 

 to place these shells in distinct genera. The loop, both in Terebratula, and Terebratulina, is remarkably 

 short ; therefore, in the former, it appears to serve the same purpose as it does in the latter, that is, in 

 principally affording support to the visceral parts, rather than the labial appendages, as in Waldheimia : 

 but the form of the loop is singularly modified, — being not much recurved, and open posteriorly, in 

 Terebratula vitrea, — and very slightly recurved, and anneliform, in Terebratulina caput-serpentis. This 

 difference, however, is easily explained on the idea, that the annular shape of the loop (or rather the presence 

 of its posterior cross-piece, to which the form of the loop is due) of the last-named shell, has resulted from 

 the complete union of the free or projecting portions of the two crural processes. 



Eudesia, p. 144. 



Mr. T. Davidson has just forwarded to me a sketch of the loop of Lamarck's Terebratula Cardium 

 fT. orbicularis, J. Sow.), which I proposed as the type of this genus. It so closely agrees with the loop 

 characteristic of Waldheimia, that I am disposed to cancel Eudesia. 



Lamellibranchiata (Perforating), p. 152. 

 Perforating bivalves appear to have existed during the Permian epoch ; as I have a specimen of compact 

 limestone from Midderidge, with perforations closely resembling those made by Pholas parva, and P. crispata 

 in limestone. Near Cong, Galway, there are several deep tubular holes in limestone, strikingly resembling 

 those made by the above terebrating shells, displaying no other apparent cause of their formation, than the 

 action of some principle in the nearly still water which they contain. They seem to point out, that a weak 

 chemical solvent, aided by very slight mechanical action on the part of the animal, powerfully contributes 

 in enabling perforating shells to make excavations in limestone rocks. 



Solemyidce, p. 1/7. 



In the page above referred to, I made the carboniferous Solemya primceva, Phillips, typical of a new genus 

 — Janeia, which I purposed reverting to in the present place, with the view of showing in what respects it 

 differed from Lamarck's genus Solemya, the type of which is the S. Australis of the same authority. But 

 I now feel convinced, from an examination of an instructive specimen of the latter species, sent me by my 

 friend Mr. Pickering, and of some casts of the former, exhibiting the muscular and cartilage impressions 

 very distinctly, that they cannot be generically separated. I was led to think, that these shells were so far 

 distinct, from the following circumstances, and from an examination of an imperfect specimen of Solemya 



