206 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxvi. 



although largely disarticulated, furnished much additional as well 

 lis corroborative information. A study of the disarticulated elements 

 of several other individuals assisted greatly in the proper interpreta- 

 tion of their arrangement. 



The predentary of Camptosaurus is as yet unknown, but as repre- 

 sented here is a modification of the Igaanudoii type rather than of 

 Ti'lceratops^ as first represented. 



A restudy of the material now available has resulted in a number 

 of modifications and changes, the more important of which may be 

 briefly enumerated as follows: 



(1) A more detailed presentation of the arrangement of the ele- 

 ments of the occipital and parietal segments. 



( 2 ) The removal j^osteriorly of the coronoid process of the mandible, 

 which alters considerably the proportionate values of the dentary 

 and the posterior elements of the jaw, that is, the lengthening of the 

 former and shortening of the latter. 



The many minor changes will be alluded to in more detail in the 

 description of the elements to follow. 



Viewed from above the skull is wedge-shaped, with the apex 

 directed forward. When seen laterally it is of moderate depth, wider 

 posteriorly than anteriorly, with a prominent orbit and large infra- 

 temporal fossa. The rami are moderately deep, but not so wide and 

 heavy as in Iguanodon. 



Basioccipital. — The heavy basioccipital is terminated posteriorly 

 by the rounded occipital condyle, which is somewhat reniform in 

 outline. In Cat. No. 5473, U.S.N.M., its greatest horizontal diameter 

 is 40 mm. and its vertical diameter 25 mm. The smooth articular 

 surface is continued forAvard on the under side of the condyle as a 

 triangular area, the apex pointing anteriorly. The continuation of 

 this articular surface would appear to indicate a greater mobility of 

 the head up and down than from side to side, at the joint with the 

 atlas. This would allow the anterior portion of the cranium to be 

 considerably depressed. 



In advance of the condyle the inferior surface is deeply concave 

 longitudinally and convex transversely, with quite a pronounced 

 median depression. Anteriorly and on either side of this depression 

 are two blunt, roughened, basioccipital processes Avhicli abut against 

 the expanded processes of the basisphenoid, the free extremities of 

 which point downward and backAvard, and underlap those of the 

 basioccipital. The basioccipital articulates with the basisphenoid by 

 a median, tongue-like anterior extension, which is received in a 

 corresponding notch on the posterior end of the latter, as in C. 

 prcsfivichii. The intercalated basioccipital process on the ventral 

 surface has a sharp median crest Avhich begins behind in a depression 

 in front of the condyle. The median superior surface is concave 



