1870.] '^Sl [Cope 



recurved. The two following (posterior to the bridge), are nearly plane 

 without recurved margin, which is slightly prominent at the point of 

 contact of the dermal suture of the marginal scuta. The posterior mar- 

 ginal bones are concave superiorly, the margin not otherwise recurved. 

 These marginals are, as usual, thickened underneath beyond the proximal 

 suture ; and into this the free end of the rib is inserted into a deep, oval 

 pit. On the terminal marginals of the bridge the pit is more distal, and 

 round. The free end of the rib springs from the costal bone at the 

 suture, and its length varies from an inch to a half an inch. The pit for 

 the hyposternal is chiefly in the last bridge marginal, partly in the first 

 free marginal. It extends along the edge of the inner thickening, as the 

 latter descends on the bridge. 



The sculpture of the costal bones consists of longitudinal shallow 

 grooves, which are more or less confluent (they are thus transverse to the 

 costal axis). On the marginals, the same ornamentation is varied by the 

 grooves being impressed punctate ; behind the dermal sutui-e, they are 

 directed slightly upwards ; anterior to it, they rise more obliquely. On 

 the posterior marginals, they are still more oblique. The sculpture of 

 the plastron is obliterated. 



M. 



Inguirral width of plastron 0.124 



Length hyposternal .08 



First free posterior marginal width 067 



" " " length - 046 



" " " greatest thickness Oil 



Corresponding costal, width 037 



" " thickrress 0045 



From the upper bed of cretaceous green saird, Burlirrgton Countj', New 

 Jersey. Discovered by my friend, Judson C. Gaskill. 

 The size of this species is about that of a snapj)ing-tortoise (Chelydra). 



HOMOROPHUS. Cope. 



Genus novum Adocidarum. 



Costal capitula wanting or rudimental. Vertebral bones of the cara- 

 pace co-ossified with the costals, sometimes, outlined on the inner surface, 

 where they appear to be lanceolate in form. The origirral costo-vertebral 

 suture, when traceable, very oblique ; the superior face of the vertebral 

 much wider than the inferior. Vertebral scuta often narrower than the 

 sujjposed outline of the vertebral bones ; on the posterior portions of the 

 carapace wanting. 



This genus is evidently allied to Adocus by the character of its costal 

 capitula, but not having the episternal nor xiphisternal bones, nor the 

 outer part of the median sternals, I cannot add other points of resem- 

 blance or difference. Tiie coossification of carapacial elements is without 

 parallel in the order, and the form of the vertebral bones prior to this 

 union, probably at an early period of life, was very peculiar. Their 



