from the London Clay. 229 



At the anterior part of the stone are seen portions of the 

 hyosternal and hyposternal bones, the entosternal and epi- 

 sternal. The hjosternal and hyposternal meet in a transverse 

 suture, and resemble in form those bones in the recent marine 

 Chelonia, differing chiefly in the much greater extent to which 

 the lateral rays approximate ; so that the deep and long emar- 

 gination usual between these bones is almost lost, Avhile the 

 distance from the front lateral margin of the hyosternal to the 

 back lateral margin of the hyposternal is of emydian short- 

 ness. From front to back, in the median line of the skeleton, 

 the hyosternal measures 4| inches ; from front to back where 

 narrowest, at the side, the same bone measures If inch. The 

 transverse width of the two hyposternal bones is about 12 

 inches ; the narrowest measurement of the right hyposternal 

 from front to back is If inch. They terminate in the middle 

 line of the skeleton, and laterally in short digitations. Unlike 

 the marine Chelonia, this animal had the internal surface of 

 these bones convex ; their external surface appears to be 

 concave. 



Between the inner anterior ends of the hyosternal bones, 

 and touched by them, extends a thin narrow bone for 2f inches ; 

 it appears to be less than an inch wide ; its anterior termina- 

 tion is not seen ; but it widens anteriorly after the usual 

 T-shaped pattern of the interclavicle. 



External to the anterior end of the right hyosternal is the 

 right episternal ; it is very thin, becomes narrower posteriorly, 

 does not exceed half an inch in width, and is exposed for 

 1| inch. 



Over the sternal bones of the right side are the coracoid, 

 scapula, and a part of the humerus. The coracoid is imper- 

 fectly preserved ; it appears to have been about 4 inches long, 

 and 2 inches wide at the distal termination, very thin, and 

 convex on the superior side ; its proportions are more in accord 

 with the Emydian type than with that of the marine Chelonians. 

 The scapula measures nearly 1^ inch from the articular sur- 

 face to the part where the scapula proper branches at about a 

 right angle from the part called the precoracoid. This latter 

 portion is small, subcylindrical, a little compressed, and about 

 2 inches long. The scapula is fractured, so that its length is 

 not known. 



So far as the remains preserved indicate affinities, the genus 

 may as well have been Chelonian as Emydian, but cannot with 

 certainty be affiliated to either type. 



Prof. Owen observes that " this carapace is understood to 



