138 



THE EXTINCT BATRACHIA, REPTILIA 



Lin. 



6.5 



.8 



The femur presents the usual constricted cylindric shaft, with trochanters whose planes -include an angle a little 



Less than 90°. 



In. 



Length of eleventh marginal, 8 



Width " " 4 



Width of a costal, '■'> 

 " " first marginal, 



Length " " 2 



" nuchal bone, •> 



" vertebral, 2 



Width 



Diameter .shaft of femur, 



15.5 



7.;j 



OSTEOPYGIS CHELYDRINTJS, Cope, Sp. nov. ' 



This large ami most distincl species was found in the same locality as the preceding. It is unfortunately only 

 represented by ten marginal plates more or less perfect, and portions of some costals, but those are sufficient to Indicate 

 some of its peculiarities. 11. combines more of the peculiarities of Chelydra in these pieces, as Euclastes docs in the 

 physiognomy of its cranium. 



The marginal bones are relatively much shorter than in any of the other species. If is however referred to this 

 genus with certainty since the anterior rib-bearing marginal bone has been united with the middle disc by suture, 

 ami some of those; posterior are ossified within the common margin of the costal and marginal scuta. The outer 

 margin of these and of the median bones of the series, is very heavy, but little produced, but projecting from a, 

 concave upper fi.ce. The inferior faces of the posterior median are convex and produced inwards further than usual, 

 and joins the inner face by an obtuse angle. The rib-pits extend deeply, or to within a, short distance of the surface. 



One posterior marginalia thicker than in 0. em argi natus and has a, convex inferior face. The upper margin 



of the inner face; is prolonged above (he lower. The rib-pit is round; the dermal suture, well marked. On. this bom; 



the character of the posterior outline is marked. The anterior half of the margin is quite concave, leaving a, strong 

 and prominent angle at the extremity of the dermal suture. This is much stronger than those; seen in Catapleura 



rcpauda, though the bom; described is more posterior than those of the latter. 



The surface of the posterior bone has some faint vascular grooves; tin; others are without them, but are of a. 

 course texture. 



Measurements. 



Length posterior marginal, 



Width 



Depth " " within, 



Width lower face middle marginal, 



Length anterior united marginal, 



Width 



Width derma] scute on same, 



Thickness costal bone, 



PROPLETJRA, Cope. 



This genus of Chelydrinae is intermediate between Osteopygis and Lytoloma, present- 

 ing more characters of the former than of the latter, so far as regards the carapace. The 

 marginal hones are free behind, except probably that the median is attached to the 

 posterior supernumerary vertebral (this piece is lost, in my specimens); and the series of 

 marginal dermal scuta are connected by a median marginal cut off from the anterior 



Tit 



I An. 



3 



0.8 



8 



o 





9.5 



i 



7.7 



2 



(i. 



1 



!). 



1 



r.s 





4. 



