AND AVES OF NORTH AMERICA. 15 



Measurements. Lines. 



Preserved length of ramus (imperfect), 11 



Depth at last tooth, 2 



Length of exposed tooth, 1.7 



Length dentary, 7.5 



Depth at coronoid, 3.5 



Do. at first tooth, 1.3 

 In the mandibular ramus of the Hylerpetou dawsoni,' there are according to Owen at least nine teetli ; in the 

 present species there are but seven. 



SAUROPLEURA, Cope. 

 Proceed. Acad. Nat. Sci. Phil. 1868, p. 215. 



This genus embraces a single species only, as I at present understand it. The 

 extremities are well developed, and the body is stout and lizard-like. It is represented by 

 but one individual which has been spread over a surface of the coal slate, exhibiting ventral 

 armature, dorsal region with ribs, and anterior and posterior limbs. Of skull and caudal 

 vertebra; nothing remains. 



The dermal riblets are arranged as in Urocordylus, i. e. in parallel lines directed 

 obliquely forwards and continuous on the median line, forming there a chevron directed 

 forwards. The stria? are not so closely placed as in O. pectinata, but are separated by 

 grooves wider than themselves. 



The humerus, idna and radius, are rather stout, and of a size relative to the body, as 

 in common types of existing sauria; the ulna and radius separate. There is no carpus, 

 but five well developed digits have phalanges in the following numbers, commencing on 

 the inside, 3, 4, 5, 6, 5. The last phalange of the second is obscured, and it is not 

 positive that the number is as given ; it is more probable than that it should have been 3. 

 The outer toe has been more slender than the others; the distal phalanges of all the toes 

 are short conic, as in Salamanders. Thus this form differs much from Ampliibamus, 

 where the numbers are 3, 3, 4, 5, 4, showing a lower development of limbs. 



The ribs are long and curved as in Reptiles, and judging by their distances the 

 vertebra? are short; the latter are not well defined but there is no indication of prominent 

 spines of any kind. 



The pelvic bones and portions of those of the hind limbs are present, but so obscured 

 and confused as not to be made out. Enough remains to show that the hind limbs are 

 considerably longer than the anterior. 



