CHELONIA. 53 



One character by which these carapaces differ from those of the Tri. Henrici or 

 Tri. Barbara is the abrupt, almost vertical, border of the carapace, which is formed 

 by the peripheral ends of the costal plates : these increasing in thickness as they 

 approach that end, render the border characteristically thick : the specific name — 

 iHcramafiis — has reference to this structure. The border is not grooved, and it is 

 slightly produced above the projecting end of the subjacent rib, where it slopes a little 

 down to the connate rib (PI. 27, fig. 1). This structure will serve to distinguish a 

 detached costal plate of the Tri. incrassatiis from one of the Tri. circmnsulcatus 

 (PI. 31, figs. 1, 2, 3) ; and the verticality and thickness of the margin will equally 

 distinguish it from one of the Tri. Henrici or Tri. Barbara. 



The chief value of the specimen (figured in PI. 26) is derived from the fact, that 

 several other bones of the same skeleton were discovered with it ; and these I next 

 proceed to describe. 



PI. 28, fig. 1, is the entosternal piece of the plastron, having the characteristic form 

 of the chevron ; it is broadest and most compressed at the median junction of the two 

 crura, which increase in thickness and diminish in breadth as they diverge. The 

 branches are relatively more slender than in the Tri. jEgjjptiacAin* and Tri. Javauicus ;\ 

 they resemble those of the Tri. carinatus\ and Tri. gangeticas.k^ 



Fig. 2 2' is the lower branch of the left episternal : it is slender, gradually tapering to 

 a point, flattened above or on the inner surface, convex behind, grooved along the margin 

 next the entosternal. This piece, in its length and slenderness, resembles the 

 corresponding part in the Tri. carinatus and Tri. gangeticus. 



Fig. 3 3' is the left hyposternal and part of the left hyosternal; the latter {lis) includes 

 the mesial border, showing the relative extent of the angular part that sends ofi"the ridged 

 tooth-like processes, which are two in number, the anterior one notched or subdivided. 

 The exterior, connate, rough, and tubcrculate dermal plate stops at the base of these 

 processes. The hyposternal (j?J4) has the nearest resemblance to that of the Tri. gangeticus 

 figured by Cuvier,|l but differs by the number of short toothed processes from its 

 median and inferior border, and by the more slender base supporting the two long, 

 lateral, striated, pointed processes. The tuberculate dermal plate covers all the 

 exterior of the hyposternal to the roots of the pointed processes. The notch for the 

 reception of the xiphisternal is rounded at the bottom. 



Fig. 4 shows the long, rib-shaped, but straight scapula (si); its head forms two 

 thirds of the glenoid cavity for the humerus ; the body, flattened behind, convex in 

 front, gradually contracts as it ascends, and terminates in an obtuse point ; the 



* Geoffroy, loc. cit., pi. 2, fig. B, o. 



t Ibid., pi. 3, fig. B, o. 



X Ibid., pi. 4, fig. B, o. 



§ Cuvier, Ossemens Fossiles, torn, v, pt. ii, pi. 12, fig. 46. 



H Loc. cit. 



