Vol. 5] Jordan.— The Fossil Fishes of California, 111 



of Isurus. The still more curved outer teeth of Isurus planus 

 are not found in the relatively small species which represent the 

 genus in the waters of to-day. These huge Miocene species must 

 have reached a length of thirty or forty feet. The present species 

 are from five to fifteen feet in length. 



It will not be possible to distinguish all the teeth of Isurus 

 tumulus from those of Isurus planus. There can, however, be 

 little doubt that we have to deal with two distinct species. 



15. Isurus smithii Jordan, new species. 



Numerous teeth from the Barker Ranch and Oil City Miocene 

 in the collection of the California Academy of Sciences differ 

 considerably from these two species of Isurus. The largest tooth 

 is more than an inch long, — slender, sharp, and flexuous. The 



Fig. 12. Isurus smithii Jordan. Miocene of Kern Count;', California. Type 

 specimen. 



base is very narrow, about two-fifths the height of the tooth. 

 Other teeth are shorter and broader, being probably from nearer 

 the side of the jaw. These teeth resemble those of Lamna clavata, 

 but they are more tapering, more sharply pointed, and without 

 basal denticle. The base of the tooth is almost equally cordate. 



