G16 GEOLOGICAL SURVEY OF THE TERRITORIES. 



tliiii, and exhibits the peculiar decussating pattern of lines of deposition 

 characteristic of tbe same layer of the dermal scuta of Crocodilians. 

 Ko portions were obtained which can with certainty be referred to the 

 carapace. The ilium is short, stout, and recurved, and the pubis is 

 largely expanded. 



AXESTUS BYSSINUS, Cope. 

 Log. cit. 



The procoracoid and scapula are of equal lengths, and the coracoidis 

 much dilated distally. 



The portions of the plastron preserved are thin for the size of the 

 animal, and all the bones are dense and smooth. The postabdominal has 

 the free margins acute and senulate. There is an external gently con- 

 vex edge, with a long process extending backward, and one long, nar- 

 row one inward. The enamel is white, and is marked with decussating 

 lines of osseous deposit, as in woven linen. This is not the result of 

 weaving. The cervical vertebra is without spine ; it is not pressed in 

 the middle, and is without any pneumatic foramen. 



Measurements. 



M. 



Length cervical vertebra 0. 01)8 



Diameter at middle OM 



Diameter at eud 0:^rj 



Diameter caudal end at ball 010 



Length OIU 



Length of an ungual phalange 043 



Proximal depth ungual phalange 013 



Length postabdominal, (broken) IdO 



Width postabdominal 120 



Locality of the last. 



TRIONtX, Geoffr. 



Trionyx hetero&lyptus, Cope, sp. nov. 



Carapace broad, flat, concavely truncate behind. Free portion of 

 costal bones short. The last pair of costal bones are in contact by a com- 

 mon suture by about two-thirds their width, the anterior portion being 

 separated by the last vertebral bone. There is a great difference be- 

 tween the sculpture of the middle of the carapace and its lateral por- 

 tions. The former region is coarsely ribbed longitudinally, the inter- 

 vening grooves being mostly' 'uninterrupted. On the mi(hlle ])ortions 

 of the costals the ridges are more or less broken up, and distally they 

 are very delicate, forming an inosculating pattern, inclosing small pits. 

 On the last costal they retain their ridge-like character. The posterior 

 vertebrals are marked by a single groove down their middle. 



Measiirements. 



M. 



Width of carapace at antepenultimate costal bone 0. 2:55 



Length from front of carapace backward 095 



AVidth of carapace, costal, distally 048 



Length of last two vertebrals 037 



Excavated from the Bridger bed, on the summit of Church Butte, by 

 the writer. 



