A NEW FOSSIL CROCODILIAN — MOOK 57 



mandibular foramen is located at the posterior end of this section 

 and the posterior end of the alveolar row at the center of the superior 

 border locates the position of the section in the ramus. Four alveoli 

 Avith bases of teeth are clearly Aasible, and a fifth or last is somewhat 

 obscure. These alveoli are much smaller than those of the maxil- 

 lary section noted above, and their height, as indicated by the 

 anterior surface of the section, is less than half that of the anterioi 

 mandibular teeth. The mandibular cavity, now indicated by matrix, 

 was large, the bony substance being thin. 



The left ramus is represented by a larger section, about 48 cm. long 

 and composed of two pieces that make clean-cut contacts with each 

 other. This section is entirely posterior to the alveolar row and in- 

 cludes the external mandibular foramen, of which the superior 

 boundary is incomplete. The posterior end of this section is near the 

 posterior end of the ramus immediately anterior to the glenoid surface. 

 The sutures separating the elements of which this part of the jaw is 

 composed are indistinct, the dentary, angular, and surangular bones 

 being almost indistinguishable from one another. 



The external mandibular foramen is unusually long and is not very 

 high. The exact relation between length and height cannot be made 

 out because of the incomplete superior border. On comparing the 

 length of this opening with that of an 84-cm. ramus of Crocodylus 

 acutus, and assuming that the proportions between the total length and 

 the length of the foramen are the same in that species and the form now 

 described, we estimate that the total length of the ramus would be 280 

 cm., or about 9 feet. Comparison with a 32-cm. ramus of Caiman 

 crocodilus indicates a total length of 172 cm., or about 5% feet, which 

 is more likely. 



One of the vertebral units is composed of the intercentrum of the 

 atlas, most of the axis, and the proximal portions of the atlas and axis 

 ribs in natural positions. The atlas intercentrum is a broad, flat bone, 

 much more distinctly bifurcated posteriorly than in C. acutus. The 

 atlas ribs attach to the bifurcations and their axes of breadth lie heloic 

 the axis and the. axis ribs. The atlas ribs are single headed, of course, 

 and are considerably thickened where they attach to the atlas inter- 

 centrum. 



The characters of the axis are not particularly distinctive except for 

 the size and strength of the processes to which the ribs are attached. 

 The ribs themselves are distinctly two-headed, the upper element, or 

 tuberculum, being slightly larger than the lower one, or capitulum. 

 The shaft is slender and is situated on edge, at right angles to the posi- 

 tion in which the atlas ribs are situated. 



Six other vertebrae are preserved, but none of them is complete. 

 Two of these united together, with a fragment of a third, are cervicals. 



