﻿188 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 102 



tubera are triradiate from their terminations, with the median portion 

 the heaviest. The foramen for the twelfth cranial nerve is located 

 beside the condyle and below the paroccipital process, at the termina- 

 tion of the posterior wing of the tubera basioccipitalia. The ninth 

 and tenth nerves exit through a dorsoventrally elongated foramen at 

 the ventral side of the jugular groove a little posterior to the median 

 portion of the tubera basioccipitalia. The fenestra ovale lies just above 

 this foramen. The foramen for the exit of the venus capitis lateralis 

 lies just above the anterior termination of the anterior wing of the 

 tubera at the bottom of the jugular groove. The foramen for the 

 hyoid branch of the seventh nerve lies at the top of the jugular groove 

 slightly posterior to the foramen for the venus capitis lateralis. A 

 thin, fairly deep ridge of bone extends downward from the paroc- 

 cipital process of the prootic so that the jugular groove is partially 

 enclosed laterally. 



The region of the hypophyseal fontanelle is so badly damaged in 

 both specimens that reliable data cannot be obtained. The basiptery- 

 goid processes of the basisphenoid are elongate and flattened as in most 

 Sautia. They are separated from the tubera basioccipitalia by a deep 

 notch, which extends to the main body of the basisphenoid. 



The anterior edge of the prootic is damaged in both specimens, but 

 enough of this region is preserved in U.S.N.M. No. 18316 to indicate 

 that the ossification of the prefacial commissure very nearly or en- 

 tirely encircled the facialis branch of the seventh nerve as it left the 

 braincase. 



A fragment of the maxilla in U.S.N.M. No. 18317 shows that the 

 anterior maxillary teeth are much smaller than the posterior teeth. 

 They increase rapidly in size to the fifth tooth, which is as large as 

 the remainder. 



The collection of Glyptosaurus material in the United States 

 National Museum, which contains most of the types, was examined 

 in connection with this material. Many of the species were founded 

 on the characters of the frontal and interorbital regions only, and as 

 yet some of the species are known only from the type specimens. 

 Although the taxonomy of a genus based on such a limited portion of 

 an animal leaves much to be desired, it is possible to make a morpho- 

 logical grouping of the species of this genus by means of the characters 

 presented by this region of the skull. Only with the aid of better 

 material can the validity of this grouping be determined. The known 

 species are tentatively grouped as follows : 



I. Interorbital region with four rows of osseus scutes with one or two odd 



scutes interpolated between the median rows G. montanus group 



II. Interorbital region with five regular, alternating rows of osseus scutes. 



Q. hillsi group 



