CHELONIA. 71 



The marginal plates (fig. 3, «, a, a) are broad, smooth, and curved evenly to the 

 edge, where they turn under at nearly a right angle. 



The second and third vertebral scutes(y2, 3) are twice as broad as they are long, the 

 outer angles being nearly right angles ; and this must be, to a great extent, a 

 permanent character, as the specimen is evidently not young. The fourth vertebral 

 scute {v\) is hexagonal, and its breadth is about one fourth greater than its length. 



Of the plastron (fig. 2), the whole of the anterior portion is wanting, including the 

 entosternal, the episternals, and a portion of the hyosternals ; and the posterior 

 portion has lost the greater part of the xiphisternals. The bones which remain form 

 a broad, somewhat convex, uniform surface. 



The most remarkable circumstance connected with this part of the osseous box is 

 the existence of a pair of intercalated, irregularly-formed bones {hp), which stand 

 between the marginal portion of the hyosternal {hs) and hyposternal bones. These 

 would appear to represent the pair of additional bones which will be seen in Flatemys 

 BuUockii (Tab. XXI), stretching across between the hyosternals and hyposternals, and, 

 in the latter case, meeting like them in the median line. 



I have examined many skeletons of Emydes, but have never observed any similar 

 structure in this genus ; but in the genus Terrapene, including the ordinary box- 

 tortoises, there appears to be, in some cases, a rudiment of a corresponding bone.* 



The total length of the carapace of this specimen, judging from comparison with 

 perfect recent examples of the same genus, was probably rather more than eight inches, 

 and its breadth is six inches. 



T. B. 



Emys Comptoni. Bell Tab. XX. 



The beautiful specimen of fresh-water Chelonia which forms the subject of the 

 present description, is in the collection of the Marquis of Northampton, who has 

 kindly allowed me the use of it, and to whose respected name I have dedicated it. 



The general form of this species, as well as many details of its structure, is so 

 similar to that of a typical land tortoise, that it is difiicult at first to reconcile its aspect 

 with the idea of its being at all aquatic in its affinities. It is, however, doubtless a 

 true Emys ; and although the present specimen is a young one, its characters are 

 sufficiently marked to enable us to distinguish it from every other. The costal plates 



* The sternal bones appear liable to occasional curious anomalous variations. Thus, while in Platemys 

 there is a perfect pair of intercalated bones between the hyosternals and the hyposternals, and in the present 

 species an approach to a similar interpolation, we find, on the contrary, in Gymnopus, a genus of Trionychidae, 

 the only skeleton of which in this country I have now in ray possession, the hyosternals and hyposternals 

 constitute but a single bone on each side, a peculiarity which I believe to be perfectly unique in the whole 

 of the Chelonian order. [T. B.] 



