MEKBIAM: THE FAUNA OF RANCIIO LA BREA. 



243 



(no. 10391 Amer. Mus. Nat. Hist.) with well worn dentition. Measurements 

 of the mandible and dentition correspond closely with those of average speci- 

 mens of C. dims from Rancho La Brea, as is shown in the table of measure- 

 ments on page 232. The mandible is exceptionally high and thick as in C. dims. 

 The massive sectorial is indistinguishable in form from that of C. dims, as 

 is also M 2 . P 4 is noticeably large compared with the corresponding tooth in 

 C. occidentalis, and in this respect resembles C. dims. The Sheridan Beds are 

 presumed to represent an early phase of the Pleistocene. 



Comparison with Material from the VaUey of Mexico. Of considerable 

 interest in connection with a study of the distribution of the American Pleisto- 

 cene fauna is the occurrence in the Valley of Mexico of remains indistinguish- 

 able from the specimens of Ganis dirus from Rancho La Brea. 



Fig. 24. Canis dirus Leidy. 

 Freudenberg. 





Posterior portion of a cranium, X 



Tequixquiac, Mexico. Adapted from 



The recent investigations of Freudenberg" have shown the existence in 

 Mexico of a varied mammalian fauna, which resembles in many respects the 

 Pleistocene fauna of the California region. Included in the assemblage are 

 several specimens of a large wolf. Photographs and a cast of the best pre- 

 served specimen 18 which Dr. Freudenberg very kindly placed at the writer's 

 disposal represent an animal which does not appear to be specifically dis- 

 tinguishable from the Rancho La Brea form of G. dirus. No remains of the 

 dentition of the Mexican type seem to have been obtained, so that a fully satis- 

 factory determination of the characters is not possible, but the close relation- 

 ship of the forms is evident from such comparisons as can be made. Especially 

 noticeable are the similarity in size, in the form of the occipital region, and in 

 the nature of the overhanging inion region (fig. 24). The last character seems 

 to be practically diagnostic of the C. dims group. In the large number of speci- 



" Freudenberg, W., Geol., u. Palae. Abh., N.F., Bd. 9, Heft 3, 1910. Die Siiugethierfauna des Pliocans und 

 Postpliocans von Mexico. 



is See Freudenberg, ibid., Taf. 6, figs. 2, 3, 4. 



