284 PALAEONTOLOGY. 



cavities in the sandstone which contained it remain, stained 

 by a deposit of an ochreous tint. The impressions are so well 

 defined, as clearly to shew that there were twenty-six verte- 

 bras between the skull and sacrum, two sacral vertebrae, and 

 thirteen caudal vertebrae, before the tail disappears by dipping 

 into an unexposed part of the matrix. Impressions of 

 twenty-one pairs of ribs are preserved, all very slender, short 

 where they commence near the head, but rapidly gaining 

 length as they are placed further back. The cervical and 

 anterior ribs are expanded, but not bifurcate, at their vertebral 

 end ; all the ribs articulate close to the bodies of the vertebrae. 

 In the crocodilian reptiles the anterior ribs are bifurcate, and 

 the posterior ones, with a simple head, articulate with long 

 diapophyses. The distinctive characters of the batrachian 

 skeleton are the double occipital condyle ; ribs wanting, or 

 very short and subequal ; a single sacral vertebra, and rib- 

 shaped ilium. The first character cannot be determined, the 

 occipital articulation not being preserved in the fossil. Instead 

 of the second character, the fossil shews ribs of varied length, 

 and most of them much longer than in the salamanders, newts, 

 or any known Batrachian. With regard to the third character, 

 the impression in the matrix clearly shews two sacral vertebrae 

 and a short sub quadrate pelvis. 



"Both the humerus and the femur shew the lacertian 

 sigmoid shape, and near equality of length, which distinguish 

 them alike from the crocodilian and batrachian orders ; they 

 are likewise, as in lizards, relatively longer than in the newts 

 and salamanders. Near the imperfect impression of the head 

 may be seen the hollow bases of some large, slightly-com- 

 pressed, conical teeth, which also tell for the saurian and 

 against the batrachian nature of this ancient reptile. I propose 

 to call it Lejptopleuron lacertinum* Many particulars of minor 

 import, bearing upon the more immediate affinities of this 



* Leptos, slender : pleuron, rib. 





