CRETACEOUS FORMATIONS. 15 



Genus, Protemys, Owen. 



In the operations of quarrying a rock of the hard variety of the gray arenaceous 

 limestone, called " Kentish Rag," which belongs to the " Green-sand " Formation, 

 near the town of Maidstone, in Kent, Mr. Bensted, the owner of the quarry, had 

 the good fortune to discover the dislocated remains of the carapace and plastron of 

 a Chelonian reptile, which remains were grouped together in a slightly dislocated 

 mass, having a circumference of three feet. This fine specimen, still unique of its 

 kind, has been liberally transmitted, by Capt. Guise, F.G.S., its present possessor, to 

 me for the purposes of being described and figured in the present Monograph. 



It represents, as will be shown in the account that follows, a distinct sub-genus in 

 the Family Emydidce, which may be characterised as follows : — 



Sternum dilatation, per yomphosin cum testa conjunctum, suturis hyo-et hypo-sternorum 

 in medio lateribusque sterni interruptis. 



Protemys serrata, Owen. Tab. VII. 



The specimen consists of the principal part of the carapace and a small part of 

 the plastron. The carapace presents an ovate form, being apparently widest about 

 two thirds from the nuchal plate. Both the nuchal (T. VII, ch) and the pygal 

 (ib., py) plates are preserved, and the total length of the carapace is 1 foot \\ inch. 

 The extreme breadth of the carapace at the part above indicated appears to have 

 been about 9 inches. The carapace is moderately convex, but becomes concave 

 near the margin of the hinder half, by a slight upward curve of the marginal plates 

 there. 



The nuchal plate is tranversely oblong, slightly but widely emarginate anteriorly, 

 3 inches 9 lines in transverse length, 1 inch 2 lines in the axis of the carapace. 

 The first vertebral scute, v l, advances within three lines of the anterior border of the 

 nuchal plate, which bears the impressions of a small nuchal scute 10 lines wide, of 

 the first marginal scute, and of part of the second marginal scute on each side. 



The first costal plate, (pi. i,) articulates anteriorly with the nuchal and first 

 marginal plates, m l, and is connate with the subjacent rib to within half an inch of 

 its pointed end, which penetrates or abuts against the third marginal plate, m 3. It is 

 impressed by the triradiate line of union of the first, » l, and second, v 2, vertebral 

 scutes with the first costal scute. The rib forms a sti'ong projection on its under 

 surface, as is shown by the impression on the left side of the carapace. The length 

 of the first costal plate, exclusive of the free end of the rib, is 2 inches 8 lines. The 

 first neural plate is lost. The second, s 2, is long and narrow, and has been, apparently, 



