148 



THE EXTINCT BATRACHIA, HEl'TILIA 



This genus was established on a species, represented by a single imperfect cranium, 

 procured by Thomas Heritage from his marl excavations, near Ilurfftown, in Camden 

 Co., N. J. The matrix in which it is preserved is very similar to that near Vincentown, 

 in which the cranium of the Thoracosaurus neocaesariensis was discovered, being a coarse, 

 granular limestone. 



The physiognomy of this large turtle in the obliquely expanded zygomata and short 

 muzzle is like the Pleurodirc genera Podocnemis Wagl. among recent Chelonia, and Bo- 

 thremys Leidy, of the same age, among extinct forms. Its completely over-arching tem- 

 poral fossae add to the impression of its affinity to-the former genus, but on inspection of 

 the vomer, it is found to be as in the true Cheloniidac, largely developed on the palatal 

 surface between the o. o. maxillaria, and to extend to a posteriorly situated tmreal open- 

 ing. Though this element is unossified in the Chelonioid types of Pleurodira, Peltoce- 

 phalus and Podocnemis, it is well developed in the family Chelydidae, (Agassi/,) and the 

 peculiarity of the cretaceous species might still exist in this suborder. As it is a mat- 

 ter of much interest to determine the precedence in time of the two suborders of the Che- 

 lonians, T have taken pains to remove the matrix from the orbital and nasal cavities, so as 

 to determine the structure of the prc-frontal bone. As I have elsewhere pointed out, this 

 sends downward a column to the vomer, either vertically or directed obliquely inwards, 

 in all the Cryptodira, while in the Pleurodira the column is wanting. 



The diagnosis will be as follows: That of the Pothremys a Hydraspid, which has fur- 

 nished the only other cranium from the same formation, is introduced. It also has the 

 vomer osseous extensively in contact with the maxillaries on the palatine surface. 



BOTIIREMYS, Leidij. 



Posterior nares separating vomer from o. o. palatine ; premaxillary margin concave, 

 involute ; alveolar profoundly concave, vomerine surface; a sulcus ; nasal meatus floored 

 in front. 



euceastf.s, Cope. 



Maxillaries and palatines separated throughout by the prolonged vomer ; posterior 

 nares opposite palatal front margin of orbits ; premaxillary margin projecting beak-like ; 

 alveolar face little concave, vomer forming a central ridge. Floor of nasal meatus perfo- 

 rate for hook of mandible. 



While Pothremys had an inferior mouth and projecting muzzle, as in the modern II y- 

 draspides, the nostrils of the Euclastes were superior and behind the short projecting beak. 

 The orbits are not, as in the Macrochelys of the Mississippi, far anterior and reduced in 



