CHELONIA. 29 



carapace are preserved in the interspaces of the beginnings of the ribs and costal plates 

 in this beautiful Chelonite. It forms part of the Fossil Collection in the British Museum. 



A carapace of a smaller individual of Chehne crassicostata, from the Harwich coast, 

 vi'ith the character of the broad and inwardly-prominent ribs strongly marked, is 

 likewise preserv^ed in the choice collection of my esteemed friend Professor Bell. 

 One of the hyosternal bones, inclosed in the same nodule of clay, testifies to the partial 

 ossification of the plastron in this species by its coarsely-dentated border ; and, at the 

 same time, shows a specific peculiarity by the convexity of that surface which was 

 turned towards the cavity of the thoracic-abdominal case. On the moiety of the 

 nodule containing the carapace and exposing its under surface, the slender rudimental 

 rib of the proper first dorsal vertebrae is preserved, in connexion with the first 

 expanded rib of the carapace. 



Besides the specimen of Chehne crassicostata from Harwich, figured in PL 21, there 

 is a mutilated carapace of a young Chehne, from the same locality, in the British 

 Museum. This specimen exhibits the inner side of the carapace, with the heads, and 

 part of the expanded bodies, of four pairs of ribs, which indicate its specific agreement 

 with the foregoing specimen, and demonstrate unequivocally its title to rank with the 

 marine turtles. It is figured in Mr. Koenig's ' Icoues Sectiles'' (pi. xvi, fig. 192), 

 under the name of Testudo plana. 



A rare Chelonite from the hard Eocene clay apparently of Harwich, in the collection 

 of my friend Frederick Dixon, Esq., F.G.S., of Worthing, shows the impressions from the 

 under surface of the carapace, and also an instructive part of the under surface of the 

 plastron itself. (PI. 22.) The proportions and degree of convexity of the under surface 

 of the costal plates of the carapace (yV, pi) correspond with those parts in the Chehne 

 crassicostata. 



The remains of the plastron include a great portion of the left hyosternal {hs), left 

 hyposternal {ps), and left xiphisternal {xs) ; the latter is articulated to the hyposternal 

 by a notch, receiving a toothed process, and, reciprocally, near the upper part of a long 

 oblique harmonia, between the outer border of the hinder angle of the h3iiosternal and 

 the inner border of the upper half of the xiphisternal. The hyosternal is concave 

 lengthwise, and is convex across on its under surface ; the transverse linear impression, 

 dividing the pectoral and abdominal scutes, crosses near its posterior border. The 

 degree of concavity of the outer surface of this bone corresponds with the convexity of 

 the upper and inner surface of the same bone in the specimen of the Chehne crassicostata 

 from Harwich, in the Museum of Professor Bell ; and it concurs with the characters 

 of the costal plates in proving the present Chelonite to be of the same species. 

 Impressions of the toothed mesial margin of the right hyosternal remain, and part of 

 the toothed margin of the left hyposternal. 



