CHELONIID^E. 215 



The type specimen (fig. 272), all that is known of the species, consists of a nuchal bone, a 

 considerable part of the first left peripheral, and a fragment of the right. 



The species is remarkable on account of the great excavation in the front of the nuchal, 

 reminding us of that of the nuchal of Allopleuron hoffmani (Gray). The individual was a 

 large one, the distance between the extremities of the nuchal being about 225 mm. The antero- 

 posterior extent of the bone, at the midline, is 105 mm. The thickness on the midline and half- 

 way between the fore and hinder borders is 25 mm. The anterior border is subacute, except 

 toward the extremities, where it becomes thick and obtuse. In the hinder border there is a 

 notch for the front end of the first neural bone. 



The border for union with the first peripheral is beveled, so that the first peripheral some- 

 what overlaps the nuchal. The suture between the two bones is a coarse one. A portion of 

 the border for union with the first costal presents a kind of tongue-and-groove joint, there being 

 on the edge of the nuchal 2 grooves and 3 slightly projecting laminae. 



The upper surface of the bone is smooth and there are no traces seen of the presence of 

 sulci. On the under side of the bone, there is, on the midline near the hinder border, an eleva- 



FlG 272 Lembonax propylceus. Nuchal and portions of right and left first peripherals. 



Type. Xj. 



tion that probably furnisht an articulation for the neural spine of the first dorsal vertebra. 

 There is no surface for articulation with the last cervical, such as is found in the living 



Cheloniidas. 



Cope referred this species unqualifiedly to the genus Lembonax and stated that it threw 

 much light on the character of the genus. As there are no carapacial bones accompanying the 

 type of L. polemicus and no plastral bones accompanying the type of his L. propylceus, it is 

 difficult to understand why they should be so confidently referred to the same genus. On the 

 other hand, it is possible that both types belong to the same species. 



Genus PROCOLPOCHELYS nov. 



An imperfectly known genus of Cheloniidx. Shell large, with thick and heavy neurals and 

 costals; two or three pairs of costals articulating each with 3 neurals. The neurals probably 

 exceeding 8 in number. First costal plate of each side suturally articulated with the nuchal 

 and the first peripheral; its rib-end entering pit in third peripheral. Large fontanels between 

 the costals and all the peripherals behind the first. 



Type : Chelonia grandteva Leidy. 



The known materials of the type of this genus lack much of yielding a satisfactory knowl- 

 edge of the characters of the genus. Nevertheless, it seems evident that Leidy's species does 

 not belong to the same genus as Chelonia mydas. Cope referred the species to his genus 

 Puppigerus; but, inasmuch as Lydekker in 1889 (Cat. Foss. Reptilia, in, p. 52) made Chelone 



