V. — Zoological Observations on a New Fossil Species of Chelydra, 



from CEningen. 



By THOMAS BELL, Esq., F.G.S. P.R.S. 



[Read January 18, 1832.] 



1 HE Testudo serpentina of Linnaeus appears long since to have been con- 

 sidered as constituting a distinct generic form by the accurate Schweigger, 

 who applied to it the name Chelydra ; but from the paper in which this di- 

 stinction was first given to the world being little known, this tortoise has 

 since received the generic appellations of Saurochelys, applied to it by La- 

 treille, of Chelonura by Fleming, and of Rapara by Gray. The last-men- 

 tioned author has, however, very properly restored the name first given to it, 

 in his St/nopsis Reptilium, the first part of which has recently appeared. 



The extraordinary length of the neck and tail, the great comparative breadth 

 of the head, and especially the shape of the sternum, sufficiently distinguish it 

 from every other form of the Testudinata. The sternum is very narrow and 

 lozenge-shaped ; and the ramus of the sternum (constituting on each side the 

 symphysis between its body and the sterno-costal suture) is exceedingly long 

 and narrow, so as to give the whole somewhat the form of a cross. 



One recent species only has hitherto been discovered, the Chelydra serpen- 

 tina ; and I cannot find any mention of fossil remains of the genus in any 

 work that I have been able to consult. The fine specimen which I will now 

 proceed to describe is, however, fortunately, sufficiently perfect to leave not a 

 moment's doubt of its relation to this genus, whilst it also retains sufficient 

 osteological characters to establish it as a distinct species. 



Of the specimen itself^, although but little of the dorsum remains, it is evi- 

 dently the upper side of the sternum which is exposed, as is shown by some 

 portions of the dorsal margin, which are still seen lying over the limbs as they 

 emerge from the carapax. This is most obvious at the part where the left 

 humerus may be observed, partly lying under the marginal extremity of the 

 anterior ribs. With this exception, therefore, the whole of the dorsal portion 

 is wanting^ having most probably been removed with the superincumbent 



* Plate XXIV. 

 VOL. v. SECOND SERIES. 3 D 



