University of California Publications. 



[Geology 



Another specimen of the same species is in the collection of 

 Dr. Rivers from the Quaternary of Rustic Canon, Santa Monica 

 Range. This specimen is about one and one-half inches high, the 

 form is narrowly triangular, the crown broader than high, the 

 point is strongly curved backward (that is, inward, toward the 

 mouth, so that the tooth seems curved upward when laid flat on a 



Fig. 13. Carcharodon arnoldi Jordan. Rustic Canon, Pescadero, California. 

 Two large specimens to left of plate. 



Galeocerdo productws Agassiz. Miocene of Kern County, California. 

 Four small specimens to right of plate. 



table). The serrae are much more fine and numerous than m 

 C. riversi, about fifty in number on the outer margin. The de- 

 gree to which these numbers are constant is yet to be proved. Dr. 

 Rivers staets that the beds in which this species is found are of 

 the same age "precisely as the hard Pecten beds of San Diego." 



The species is named for Dr. Ralph Arnold of the U. S. Geo- 

 logical Survey. 



