150 University of California Publications in Geology [Vol. 10 



of the first tooth in Nothrotherium the deeply concave, outer wall of 

 mandible between M T and Mj, occurring in Hapalops and Megalonyx, 

 becomes greatly reduced and may be entirely absent as in no 166. 

 There are frequently two foramina representing the postero-external 

 opening of the dental canal in the Raneho La Brea species. In no. 208 

 two foramina are present on the left ramus and one on the right, an 

 occurrence similar to that in a skull of Hapalops longiceps, no. 15523 

 Prin. Univ. Coll., wbile in no. 456 from Raneho La Brea there are 

 two foramina on each side. The anterior foramen is situated on the 

 outer surface of the ramus opposite the last inferior tooth and the 

 second opening is at or slightly above the base of the ascending process. 



The eoronoid process arises well to the outer side of M 3 as in 

 Hapalops. but it is relatively smaller than in the latter. It may be 



Fig. 6. Nothrotherium sJiastense Sinclair. Mandible no. 166 M. IT. S. A., 

 lateral view, X %. Raneho La Brea Beds, California. 



broad as in no. 456 or rather narrow. The sigmoid notch, due to the 

 high position of the condyle above the tooth row in Nothrothevium, 

 is relatively much smaller than in the Miocene genus. In no. 208 the 

 condyle in dorsal view has much the shape seen in Hapalops longiceps. 

 In no. 456 and no. 418 the condyle has a greater oblique diameter and 

 is more slender than in no. 208. The ventral notch between cond.yle and 

 angle is relatively wider than in Hapalops, while the angular process 

 in some specimens from the asphalt extends posteriorly as a more 

 slender hook than in H. longiceps. The angle of the jaw is much more 

 slender in Nothrotherium than in Megalonyx. In M. jeffersoni the 

 eoronoid and angle are more nearly equally spaced on either side of 

 the condyle than in the Raneho La Brea genus. The inferior border 

 of the angle is deflected inward, forming a more pronounced shelf 

 than in Megalonyx. 



