AN!) AVES OF NORTH AMERICA. 



129 



It also possesses a character of Pleurostermim in the presence of a series of marginal 

 dermal plates on the sternal bridge. It belongs to the true Emydidae, having the eight 

 paired sternal bones instead of ten of the first mentioned. The markings of the dermal 

 plates of the plastron are not distinct. 



ADOCUS BEATUS, Leidy. 



Emys beatus, Eddy, Cretaceous Reptiles, Bmithson, Contrib, 1804, 107. 



Remains of a considerable portion of the plastron and carapace of this species from 

 the marl excavations of David Haines near Medford, N. J., furnish important characters, 

 as already indicated. The posterior lobe of the sternum is long and flat, and strongly 

 emarginate behind; its greatest length is 5 in. 9 lin., greatest (anterior) width 5 in. 8 lin. 

 The; thickness of the hyostcrnal bones is a little greater at the sides than at the median 

 portion ; latter measurement 7 lines ; all the pieces of the plastron are thicker than those 

 of the carapace. 



The anterior lobe of the sternum in A. beatus would appear to have been more or 

 less moveable. 



ADOCUS TRAVUS, Leithj. 



Emys prctvuB, Leidy, Proceed. Ac. Nat. Soi., 18. r >fi, 312, Cretaceous Rept. Tab. 

 Middlebed, or upper Cretaceous green sand New Jersey. 



This species is referred here because of its general resemblance to the others of the 

 genus. Its costal bones have not yet been procured. 



PLEUROSTERNUM, Bell. 



Some of the Emydinae of the New Jersey Green Sand exhibit only faint impressions 

 of the usual horny dermal plates. It is probable therefore that such, were covered 

 with coriaceous plates as in the genus Dermatemys and some species of Ilydraspididae. 



The species which is referred to Dermatemys, I), mavei Gray from Mexico, is further 

 distinguished generically by a series of marginal plates between the axilla, and groin on 

 each side, within the usual marginal series. The same peculiarity characterizes also the 

 genus Macrochelys, which has however no affinity with the present. 



The hyostcrnal bones, quite perfectly preserved, of an aquatic tortoise, from the farm 

 of David Haines near Medford, present the double marginal series of Dermatemys. It 

 differs from the species of that genus in the apparent fusion of the pectoral and humeral 

 dermal scuta, a peculiarity which I have not seen in any modern genus of Emydidae or 

 Ilydraspididae. Tins is characteristic of Pleurostcrnum, and the scuta are really distinct, 

 the pectoral having an unusually posterior position, on account of the intercalated sternal 



AMEEl. PHILOSO. SOC. — VOL. XIV. 33 



