27 



A portion of the left dentary bone containing alveoli for ten teetli 

 shows that this species is not a gavial. The dental series passes in a 

 curve from the inner to the outer sides of the bones, one or two alveoli 

 behind being probably bounded on the inner side by the splenial only, 

 as in B. macrorhyncJms, when that bone is in place. The dentary is 

 compressed at this point ; in front it is depressed. There is a slight dif- 

 ference in the sizes of the alveoli, but not sucli as is usual in Tertiary 

 crocodiles. The external face of the bone exhibits deep pits in longi- 

 tudinal lines. The angle of the mandible is depressed 5 the cotylus of 

 articulation is partially concealed on the outer side by the elevation of 

 the surangular, whose upper border is parallel with the inferior margin 

 of the ramus for two inches to where it is broken off. The outer face of 

 this region marked by irregular coarse ridges more or less inosculating, 

 separated by deep pits. The lower posterior half of the angular bone is 

 smooth. 



A posterior dorsal or lumbar vertebra has a depressed cordate articular 

 cup. The zygapophyses are large and widely spread and strengthened 

 by obtuse ridg.es running from the base of the neural spine to the pos- 

 terior margin of the anterior and the posterior outer angle of the pos- 

 terior. One pit at basis of neural spine in front; two before. Ball 

 prominent ; sides of centrum concave. 



Measurements. 



M. 



Length of fragment of ramus lOQ 



Width in front - 034 



Depth behind 032 



Length of eight alveoli 069 



Diameter of largest alveolus 012 



Diameter of smallest 007 



Width of base of angle of ramus 048 



Depth at surangular 034 



Length of centrum of vertebra 045 



Width of articular cup 031 



Vertical diameter of cup 025 



Vertical diameter of neural arch Oil 



Expanse of anterior zygapophyses 056 



The specimen is adult, and indicates an animal about the size of the 

 alligator of the Southern States. Its reference to the present genus is 

 provisional only. 

 BoTTOSAURUS(?) HUMiLis, Leidy. Crocodilus humilis, Leidy. Proceed. 



Acad. Kat. Sciences. Phila. 1856, p. 75. (Teeth only.) Bad lands of 



Montana, (Judith Kiver.) 



SAUEOPTERYGIA. 



POLYCOTYLUS, Cope. 



PoLYCOTYLUS, LATIPINNIS, Copc. Extiuct. Batr. Reptilia N. Am. 1869, 

 p. 36, Plate I, Figs. 1-13. Hayden's Geol. Survey, Wyoming, 1870. 

 p. 388. 

 From the Niobrara chalk of Kansas. 



