GEOLOGICAL SUKVEY OF THE TERRITORIES. 615 



size, while one behind the middle of the maxillary is larger than the rest. 

 The posterior teeth have short, very obtuse crowns, with elliptic fore and 

 aft ontlme. They resemble some forms seen in Pycnodont fishes, and 

 are closely striate to a line on the apex. The upper surface of the cra- 

 liium is pitted, the frontal and parietal bones with large, deep, and 

 closely placed concavities. The former is perfectly plane, and the latter 

 is wide. The squamosal arch is also wide, and the crotophite foramina 

 are large and open. 



The dermal scuta are very large for the size of the animal, and were 

 not united by suture. They are keelless and deeply pitted, with smooth 

 margins. 



The vertebral centra found with other specimens are round. The 

 co-ossified neural arches indicate the adult age of the animal. 



Measurements. 



M. 



Height crown premaxillary tooth 004 



Width crown premaxillary at base OOSS 



Long diameter crown of a maxillary 005 



Short diameter crown of a maxillary 0035 



Width parietal 009 



Width frontal, posterior 020 



Width frontal, interorbital 010 



Width malar below eye 008 



The variation in the form of the teeth is a slight exaggeration of that 

 seen in the dentition of various species of crocodilians. 



This species was about three feet in length, found by the writer in 

 one of the lowest beds of the Green Eiver Tertiary epoch, near Black 

 Buttes, Wyoming. 



The dermal scuta of thisspecies are very abundant in some of the 

 beds of the Green Eiver epoch. Some of them exhibit a faint trace of 

 keel. Vertebr£e associated with them have subround articular ex- 

 tremities. 



TESTUDINATA. 



AXESTUS, Cope. 



Proceed. Amer. Philos. Society, 1872, j). 462. (Published July 29.) 



This is a genus of Trionychidse, which is represented by a species not 

 fully known. The type specimen is represented by bones of the limbs 

 and various vertebne, with the postabdominal bone of the left side. 



The general characters are those of Trionyx. The scapula is elongate, 

 the procoracoid long and narrow, and the coracoid of medium width. 

 The humerus is sigmoid, with widely spreading bicipital ridges and flat- 

 tened extremity with marginal groove. The femur is also curved, but 

 less strongly than the humerus, and has a median anterior low angular 

 ridge. The claws are large, some curved and some entirely straight. 

 The cervical vertebra; are relatively large and elongate. The two sacrals 

 are free from the carapace above, have broad articular surfaces for 

 diapophyses, and flattened centra. The caudals are proccelian, and have 

 short diapophyses. The postabdominal bone has somewhat the form 

 seen in existing Trionyx. It presents two dentate processes forward 

 for the hyosternal, and two inward to its mate in front. It is- pro- 

 longed backward and inward into a flat process. It is especially dis- 

 tinguished by its tenuity, and the entire absence of the suijerficial 

 sculjjture of' Trionyx, The usual dense layer is present, but is quite 



