CROCODILIA. 165 



edges not serrate. Those of tlie premaxillary bone are subequal in 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 

 outline. They resemble some forms seen in Pycnodont fishes, and are 

 closely striate to a line on the apex. The upper surface of the cranium 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 crotaphite foramina are large and 

 open. 



The dermal scuLa 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 

 coossified neural arches indicate the adult age of the animal. 



Measurements. 



Height of crosvn of premaxillary tooth 004 



Width of crown of premaxill.ary tooth at hase 0035 



Long diameter of crown of a maxillary 005 



Short diameter of crown of a maxillary 0035 



AVidth of pariet.al 009 



Width of frontal, posterior 020 



Width of frontal, interior orbital 010 



Width of m.alar below the 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. 



The axial portion of the basioccipital bone is a transverse vertical 

 plate with vertical carina on the distal half. The frontal bone exhibits no 

 ledge or crests, and the crotaphite foramina are open. The quadratojugal 

 arch is stout. The dermal scuta are not united, and with the cranium, are 

 deeply pitted. They are very abundant in some of the beds of the Green 

 River epoch. Some of them exhibit a faint trace of keel. Vertebrae asso- 

 ciated with them have subround articular extremities. 



This is the smallest North American species, and is as small as any mem- 

 ber of the genus that is known. It did not probably exceed three feet in 

 length. I only found it in the beds of the Wasatch or perhaps Green River 

 epoch, south of Black Butte, Wyoming. A species of similar proportions 



