1917] 



Stock: Skull and Dentition of Nothrotherium 



141 



by Reinhardt 13 differs noticeably from the Californian form in dorsal 

 contour of skull (fig. 2). It is possible that this difference is in part 

 due to age, but it is probably a specific distinction. In Hapalops 

 longiceps the frontal is more elevated than the parietal, while in H. 

 vulpiceps and H. graciUdens the reverse is true, the parietal being 

 much more highly vaulted than the frontal. In the elevation of the 

 frontal the Rancho La Brea species of Nothrotherium approaches 

 Planops most closely. MegaLonyx differs from its Pleistocene con- 

 temporary in the straight dorsal contour of the skull. 



The zygomatic process of the squamosal is long and slender. It is 

 relatively longer than in H. longiceps. In skull 15, used as the type 

 in the first description 14 of the species from Rancho La Brea, this 



Fig. 2. Nothrotherium sliastcnse Sinclair. Cranium, no. 208 M. H. S. A., 

 lateral view, X %• Rancho La Brea Beds, California. 



process is broken. The malars have been preserved in several skulls, 

 notably in no. 208, where they are firmly attached at the base to 

 lachrymal and maxillary. The malar resembles Hapalops in slender- 

 ness, and, as in that genus, is not fused with the zygomatic process of 

 the squamosal. It differs from H. longiceps in (1) its relatively shorter 

 anteroposterior extent, (2) an absence of a marked outward flare of 

 the infraorbital border, (3) a shorter dorsal prong, but deeper notch 

 for the zygomatic process of the squamosal, and (4) a relatively longer 

 and more slender ventral prong. 



13 Reinhardt, J., Kaempedovendyr-Slaegten Coelodon, Vidensk. Selsk. Skr., 

 5 Raekke, naturvidenskabelig og mathematisk Ar'handl., vol. 12, 3, pp. 253-310, 

 5 pis., Copenhagen, 1878. 



i-t Stock, C, op. cit., pp. 342-350, 1913. 



