70 SYSTEMATIC PALEOXTOLOGY 



Measurements. 



Length of the body from the bottom of the con- 

 cavity to the summit of the convexity 3^ inches (81 mm.) 



Length laterally, exclusive of the convexity, has 



been about 3^ inches (81 mm.) 



Vertical diameter of convexity has been about. . . .3 inches (75 mm.) 



Transverse diameter of convexity has been about. 3 inches (75 mm.) 



Transverse diameter of body at middle from one 



lateral suture to the other 2^ inches (56 mm.) 



" The fragment of rib consists of the vertebral third of one of the 

 posterior ribs. It is thick and strong in accordance with the size of 

 the animal, but presents nothing peculiar. 



" The ungual phalanx appears, so far as I can ascertain from com- 

 parison with those of Alligator lucius, to be the first of the thumb. 

 It is of large size and very robust. Its base is trilateral with rounded 

 angles, and presents a transverse concave articulating surface. The 

 depressions for the lateral ligaments just above the condyles are re- 

 markably deep. Just postero-superiorly to one of the depressions is 

 an oval tubercle for tendinous attachment. 



Measurements. 



Length of phalanx 3^ inches (56 mm.) 



Greatest breadth at base 15 lines (30 mm.) 



Greatest depth of base 13 lines (26 mm.) 



Breadth of condyles 10| lines (21 mm.) 



" For the species to which the fragments of the skeleton described 

 belonged, I propose the name Crocodilus antiquus." 



Occurrence. — Chesapeake Group. High Cliffs of the Potomac river, 

 40 miles above the mouth of the river in Westmoreland county, Virginia. 



Collection. — The specimens consist of two teeth, two vertebrae, a 

 fragment of a rib and an ungual phalanx. They are in the Museum of 

 the Academy of Natural Sciences of Philadelphia. 



