234 



THE EXTINCT UATRACHIA, KEPTILIA 



posterior vertebral bones. The posterior marginal bones are not revolute. The costal bones are delicately grooved in 

 the length of the carapace. The anterior extremity of the anterior sternal lobe is narrowed, prominent and truncate. 

 Length of the whole animal about two feet. 



Found near Ft. Bridger, Wyoming Territory, by Dr. Van Carter. 



The genus Baptemys to which this species is referred by Leidy, appears to be the same as Adocus. 



Adocus pravus, Leidy. 

 Emyt prawn, Leidy, Proo. Ac. Natl. Sei. Pbila., 1658, 808. Cretaoeous Rept. U. S., 108. Adorns pram,,*, Cope, 



Synopsis Hair. Rept. N. Am., 129. 



This species is as yet known only from the original specimens, in the collection of the Geological Survey of New 

 Jersey. The plastron is thinner than in the three preceding, and the hyosternals embrace the mesosternum extensively. 

 This distinguishes the species from A. agilis, where the mesosternal emargination is much wider than deep. Width ol 

 anterior lobe of sternum at epi-hyosternal suture, four inches. 



Upper bed of Cretaceous Green sand, New Jersey. 



Adocus agilis, Cope. 

 Geological Survey of New Jersey, App. C, p. 7*14. 

 Represented chiefly by an almost complete plastron from the excavations of the West Jersey Marl Company, in 



the upper bed of the upper Cretaceous Green Sand of New Jersey. 



This specimen belonged to an individual of larger size than any heretofore referred to the genus, and one charac- 

 teristically ornamented by a peculiar sculptm-o. 



The extremities of both lobes are broken oil'; the margin of the posterior is thinned out, and carries an aeuteucss 

 of edge to the inguinal notch, where the margin is quite thick. The outline ol' the caudal scuta, is very convex ante- 

 riorly; that of the femorals is gently convex towards the front. The suture between the hypo- and xiphistemals is 

 nearly transverse below; on the upper face it sends a. process int.. the hypostemals forwards, which is acuminate; the 

 hyposternals send a, marginal process backwards beyond the line of the median suture, which is squarely truncate; its 

 outer edge is the margin of the bone. The impressions of contact of the pubes are well marked; they are strongly in- 

 curved, and are not very different from those seen in Cistudo. The bridge of the plastron is preserved, and furnishes 

 attachment for three marginal bones; perhaps fractions of others also. The suture between the abdominal andhu- 

 meral Bouta is convex backwards, and unites with an Inner angle of the anterior ol' the inter-marginal series of the 

 bridge. There are three in flit! latter series, all longer than broad, but the middle one relatively much narrower than 

 the ..i hers, as it is six times longer than wide, with parallel sides. That anterior to it is more hexagonal and wider, pre- 

 senting an angle inwards for union with the suture between the abdominal and humeral scuta. 



About half the mesosternal bone is preserved. It is a, transverse diamond with truncate extremities. Its poste- 

 rior angle is, therefore, very open, but is not rounded. No suture bounding either humeral or gular scuta is visible 



on it; the anterior angle is broken away. The anterior portion of the ephisterna! bone preserved has a, regular con 

 vex outline, and the sculpture of the inferior surface is a slight Imitation of that seen in some species ol' Trionyx. It 

 is closely shallow-punctate, or like small rain-drop impressions. These are irregularly distributed on the anterior 

 part of the plastron, ami on the posterior lobe in obliquely decussating series. 



Afeamrementx. 

 M. M. 



Width of plastron at bridge, 



Length between mesosternum and xiphisternum, 

 Width posterior lobe at Inguinal notch, 



" mesosternum, 

 Length " 



" hyosternum medially, 

 Thickness " " 



0.2879 



0.31 



0.1885 



0.(101 



0.0005 



0.0!) 



0.012 



M. M. 



Thickness hyosternum at marginal suture, 0.007 



Length abdominal suture, 0.1068 



femoral " 0.087 



" median intermarginal suture. 0.0825 



Width " " " 0.015 



Estimated length plastron, 0.45 



" carapace, 0.56 



