12 NATURAL HISTORY 



mine for this article; and though I was disappointed 

 as to the fossil, I was highly gratified with the sight of 

 several of the shells themselves in high preservation. 

 This bivalve is only known to inhabit the Indian ocean, 

 where it fixes itself to a zoophyte, known by the name 

 Gorgonia. The curious foldings of the suture the one 

 into the other, the alternate flutings or grooves, and 

 the curved form of my specimen being much easier 

 expressed by the pencil than by words, I have caused 

 it to be drawn and engraved 2 . 



OSTRKA CAR1NATA. 



a Notwithstanding the great care which was evidently bestowed by 

 the author on the identification of his fossil shell, he was by no means so 

 successful in the results of his research as he deserved to be : it is cer- 

 tainly not the analogue of the cock's comb oyster, the Mytilus Crist a. 

 Galli of Linnaeus and Ostrea Crista Galli of Lamarck ; but belongs to an 

 altogether different species which has not, so far at least as conchologists 

 yet know, any living analogue. The figures given above, which are 

 copied from those of the original edition, represent a shell of the species 

 to which, on account of the strong ridge or keel along the middle of 

 each of its valves, Lamarck gave the name of Ostrea carinata. It has 

 repeatedly been figured, since the first publication of the Natural History 

 of Selborne, as well in foreign as in English works: and, by a curious 

 coincidence, in the Genera of Recent and Fossil Shells, by Mr. G. B. 

 Sowerby, one plate contains representations both of this fossil (from a 

 gigantic specimen) and of the cock's comb oyster, to which Gilbert White 

 referred it. Though both are plaited oysters, the plaits or folds are 

 disposed in a manner altogether dissimilar in the two shells : in the 

 cock's comb oyster they are in the longitudinal direction of the shell, 

 which, moreover, is rounded in its general outline ; in the keeled oyster 

 they pass transversely on each side from a ridge which is continued 

 along the middle of a considerably produced shell. 



The statement in the text, that it was obtained in the chalky fields, 

 renders it necessary to caution the reader against regarding it as a chalk 



