50 MAURICE G. MEHL 



pits are shallow and varying in size, for the most part minute, 

 but well defined. 



The relations of the various bones of the skull are quite alli- 

 gatoroid, as are their general proportions with few exceptions. 

 The prefrontal is relatively longer than in the genus Alligator and 

 extends at least half the length of the lachrymal, in advance of the 

 latter element. The nasals are relatively broad, the two making 

 nearly half the total width of that part of the skull. 



Unfortunately, part of the anterior border of the snout is miss- 

 ing, but the portions present are sufficient to show some of the 

 important characteristics. Unlike the condition in all the true 

 alligators, the nasals, while projecting slightly into the external 

 narial opening, do not form a more or less complete bony septum. 

 Furthermore, the premaxillae do not form an arch over the anterior 

 border of the opening as is the case in all modern and extinct alli- 

 gators with one or two exceptions, perhaps. In this respect, the 

 skull simulates that of Brachychampsa Montana, an alligatoroid 

 form described by Gilmore from the Upper Cretaceous of Montana. 1 

 To quote: "In the absence of a roof-like covering formed by the 

 premaxillaries over the anterior part of the external nares, Brachy- 

 champsa differs from all known alligators, both recent and extinct." 



The anterior border of the nares in the described form differs 

 from that of Brachychampsa, however, in that the premaxilla in 

 the former are still further reduced till the nares are directed 

 slightly forward and lack entirely the definite ridgelike anterior 

 border. This is the condition pointed out by Loomis in a specimen 

 described by him from the Oligocene of South Dakota and referred 

 to the genus Crocodilus. 2 Quoting Loomis on this point: "The 

 undivided nasal opening is very far forward, and differs from that 

 of the other crocodiles in the lack of a distinct anterior border, this 

 portion of the nasal cavity having a smooth, rimless boundary 

 on the premaxilla. The nostril opening would seem, therefore, 

 to have been directed to the front, rather than upward on the snout. 



1 "A New Fossil Alligator from the Hell Creek Beds of Montana," U.S. Nat. 

 Mm., XLI (1914), 299. 



2 "A New River Reptile from the Titanothere Beds," Am. Jour. Sci., CLXVIII 

 (1914), 429. 



