250 PALEONTOLOGY 



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

 well defined, as clearly to show that there were twenty-six 

 vertebra? between the skull and sacrum, two sacral vertebrae, 

 and thirteen caudal vertebra?, 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 vert el »ral 

 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 shows 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 shows two sacral vertebrae 

 and a short subquadrate pelvis. 



"Both the humerus and the femur show 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-compressed, 

 conical teeth, which also tell for the saurian and against tin 1 

 batrachian nature; of this ancient reptile. I propose to call it 

 Leptojplmron lae&rtinv/m,. Many particulars of minor import, 

 bearing upon the more immediate arnnities of this most rare 



* Af7TT(k. slender; -nk(vp6v, rib; for tin's compound we have the authority of 

 Poikilopleuron, already applied to an extinct gfnus of Bauriane. 



