22 . FOSSIL FISHES OF SOUTHERN CALIFORNIA 



11. Carcharodon rectus Agassiz. 



This species of the Kern Miocene seems to differ from CARCHARODON 

 ARNOLDI, by the presence of a small, blunt, lateral denticle at base on 

 each side. It is not common. 



12. Carcharodon arnoldi Jordan. 



(Plate VIII, fig. 1) 

 (CARCHARODON RIVERSI Jordan) 



Two very perfect teeth of the form called CARCHARODON ARNOLDI 

 (No. CXXVIII) were found in the shales of the upper Pliocene at 

 Fourth and Hill Streets, Los Angeles. These are slightly flexuous with- 

 out distinct median ridge, no basal denticle, and about forty-five sharp 

 serrations on each side, these serrations extending to the tip. 



From deposits Miocene or Pliocene in Orange County we have 

 also seven specimens of sharks' teeth corresponding to the type of 

 CARCHARODON RIVERSI. The type of this species is from the Santa Monica 

 range near Santa Monica. Another is from Port Los Angeles in rock 

 regarded by Dr. J. J. Rivers as of Pliocene age. 



The essential feature of CARCHARODON ARNOLDI lies in the small 

 number of the serrations, thirty to fifty on each side, the teeth being 

 small and of varying width, some (outer) being much narrower than 

 the median teeth. There is no median ridge on any of these teeth. One 

 very small (outer) tooth is very narrow and flexuous, looking like a 

 tooth of ISURUS, but it has about thirty serrae on each side, while the 

 teeth of ISURUS are smooth-edged. 



It is on the whole likely that C. RIVERSI represents outlying or 

 imperfect teeth of the species called CARCHARODON ARNOLDI. 



13. Carcharodon megalodon Charlesworth. 

 (CARCHARODON BRANNERI Jordan) 



This giant shark was described in the University of California Publi- 

 cations, Geology, 1907, p. 116, as CARCHARODON BRANNERI, the type 

 being from Bolinas Bay, Marin County, the co-type from Santa Ana, 

 Orange County. We have examined others from the Miocene of Kern 

 County. . 



The sole difference between C. BRANNERI and the still more huge 

 C. MEGALODON from South Carolina and elsewhere, lies in the smaller 

 number of serrations on the teeth of C. BRANNERI, there being 80 to 100 

 on each side, and 100 to 120 in C. MEGALODON. Later comparison makes 

 this distinction doubtful, the median teeth having more serrations than 

 the smaller outer ones. 



