CHELONIID®. 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 4/lopleuron hoffmani (Gray). The individual was a 
large one, the distance between the extremities of the nuchal being about 225mm. 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 lamine. : : 
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- 
Fic. 272.—Lembonax propyleus. Nuchal and portions of right and left first peripherals. 
Type. X#. 
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 
Chelonidz. 
Cope referred this species unqualihedly 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. propyleus, 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 Cheloniida. 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 grandeva Leidy. 
The known materials of the type of this genus lack much of yielding a satistactory 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, 111, p. 52) made Ch 
