1917] 



Stock: Skull and Dentition of Nothrotherium 



139 



Museum of History, Science and Art of Los Angeles. For the privilege 

 of studying this remarkable collection of nothrotheres, I am very 

 greatly indebted to Director Frank S. Daggett, Thanks are due also 

 to the other members of the Museum staff for many courtesies extended. 

 I am obligated to Professor John C. Merriam for assistance and much 

 friendly advice and criticism during the progress of the research on 

 the Rancho La Brea edentates. 



The drawings reproduced in this paper have been prepared by 

 Mrs. Louise Nash. 



CEANIUM 



The largest available skull of Nothrotherium from Rancho La Brea 

 is approximately as long as a skull of Megalonyx jeffersoni described 



Fig. 1. Nothrotherium shastense Sinclair. Cranium, no. 208 M. Ii. S. A., 

 superior view, X %. Rancho La Brea Beds, California. 



by Leidy. 8 With this exception the specimens from the asphalt beds 

 are all somewhat shorter than either M. jeffersoni or M. leidyi. In 

 marked contrast to Megalonyx, however, is the relative slenderness of 

 skull in Nothrotherium. In this respect the latter genus more closely 

 resembles the Miocene Megalonychidae and Planopsidae," from which 

 it has also deviated less than Megalonyx in general shape of skull. 

 Contrasted with Planops, one of the largest of the Santa Cruz Gravi- 

 gracla, the skull of the Pleistocene genus is distinctly larger. 



s Leidy, J., A memoir on the extinct sloth tribe of North America, Smithson. 

 Contrib. Knowl., vol. 7, 1855; see measurements of the Dickeson specimen, p. 13. 



8 Scott, W. B., Rept. Prin. Univ. Exp. Patag., 1896-1899, vol. 5, p. 164, fig. 16, 

 1903. 



