262 



Annals of the Carnegie Museum. 



which is smaller and deeper. The post-tympanic is very different from 

 that of Aphelops montanus. It is not rounded antero-posteriorly, but 

 is wing-like, expanding antero-externally. It is quite thick antero- 

 posteriorly. 



Measurements will be found in the original description of A. 

 ceratorhinus. 



Aphelops ceratorhinus ? 



Carnegie Museum Catalogue of Vertebrate Fossils, No. 854. 

 This specimen consists of the posterior portion of a skull. The 

 posterior basal portions of the crania are preserved both in this speci- 

 men and in the type of Aphelops ceratorhinus and the corresponding 

 parts agree in all essential particulars, though, as would be expected, 

 there are some minor differences. 



The occiput is moderately high for the width and narrows upward 

 as in Aphelops megalodus. The supraorbital ridges unite for a short 



distance forming one low narrow 

 ridge which represents the sagittal 

 crest. The paroccipital processes and 

 the post-tympanics are essentially like 

 those of the type of the species. The 

 former have deep posterior concavities 

 in the bases, and a prominent ridge 

 extends, external to the cavities, from 

 the posterior portion of the processes 

 to the base of the occipital condyles. 

 The anterior faces of the paroccipital 

 processes are trough-shaped. The 

 post-tympanics are not so large and 

 rugose as in the type. The external 

 auditory opening is long, comma- 

 shaped, and below this the post-tym- 

 panic and post-glenoid processes are 

 nearly in contact for some distance. 

 The median basal portion of the skull 

 has a nearly flat area between the occipital condyles and anterior to 

 them. Anterior to this is a high, narrow, median ridge in front of 

 which there is a rounded knob, or protuberance, just posterior to the 

 pterygoid fossa and between the glenoid articular surfaces. 



Fig. 5. Lateral view of back of 

 skull of Aphelops ceratorhinus? \. 

 (No. 854.) 



