316 University Geological Survey of Kansas. 



This difference is well illustrated by comparing the types of 

 Saurocephalus dentatus and Saurodon ferox; the maxilla of the 

 first is considerably longer than that of the second, but with 

 the dentaries the reverse is the case. Only a small portion of 

 the dentary can be seen, as most of the external and superior 

 portions are hidden by the overlying maxillse. The bones are 

 irregular and shallow at the symphysis and seem to have given 

 strong attachment for the predentary. The lower border is 

 thin and sharp. Only twenty-seven millimeters of the alveolar 

 border can be seen in the specimen, upon which the teeth are 

 small and twelve in number. At the base of each tooth is found 

 the deep notch for the nutrient vessels, so characteristic of this 

 genus. As the articular portion does not seem to differ materi- 

 ally from that of S. ferox, its description may be deferred. 



Contrary to anticipations, there is but one predentary, as is 

 proven by the discovery of all of the parts in place. It is long 

 and slender, triangular in outline, with a broad, elliptical articu- 

 lar surface at the posterior extremity. When this element was 

 first made known 76 in this genus, I was under the impression 

 that it was paired, which is not the case. This slender pro- 

 jection was no doubt used as a weapon of offense, analogous to 

 the rostrum of Protosphyrsena. In connection with the descrip- 

 tion of Saurodon broadheadi 77 I figured a predentary of an en- 

 tirely different form from the above, which was found on the same 

 slab with the maxilla described ; the form is the same as that 

 found in Saurocephalus. Whether the two bones belonged to 

 the same individual or not only future discoveries can deter- 

 mine. After carefully comparing the type of S. dentatus with 

 that of the species under consideration and S. ferox, I am con- 

 vinced that there is but one predentary in the mandible of this 

 form, as one would expect from the great similarity of the two 

 genera. 



Mandible : Length from cotyloid cavity 155 mm. 



Depth at symphysis 23 " 



Number of teeth in one centimeter, 4.5. 



Predentary : Length (estimated) 73 mm. 



Depth of symphyseal surface 23 " 



Width of symphyseal surface 12 " 



76. Kans. Univ. Quart., vol. VII, p. 24. 77. 1. c, pi. II. 



