ii8 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES. 



was found by the writer in Pliocene ? deposit of Sonoma 

 County. 



HIPPOPOTAMUS 



A fossil tooth of a hippopotamus, or closely allied animal, 

 was found with the last named rhinoceros. Both specimens 

 are in the Yates Collection. 



BEAR 



The late Professor E. D. Cope found remains of an extinct 

 bear in a cave in the limestone of Shasta County, California; 

 It was as large as the grizzly ; he named it Arctotherium simum. 

 Its teeth differed from those of living species. 



PORPOISE. 



Fossil remains of the porpoise (Delphinus), similar to the 

 living species, have been found by the writer and others, at 

 various points near the coast, from Santa Barbara to Half- 

 Moon Bay, San Mateo County, in Pliocene and Quaternary 

 lormations. 



CONCERNING FLEAS. 



BY PROF. J. J. RIVERS. 



Fleas, like all other true insects, pass through stages of 

 development. Starting Avith the egg, which yields a larva, or 

 grub, this continues toward maturity and when fully fed spins 

 a cocoon, as does a silkworm, and assumes the chrysalis state. 

 After a period of rest and ripening the tenant of the cocoon 

 gives up the dormant period of its life and becomes a lively 

 example of its class— a flea. 



To entomologists a large number of different species are 

 known, but the common tormentor is not the human flea, Pulex 

 irritans, L., but the flea of the dog and cat, Pulex serraticeps, 

 Cerv. 



There are curious opinions as to the causes that produce 

 fleas. Some persons aver that they breed in the sand by the 

 sea shore, as they have often seen them in great numbers in 

 such situations; other persons contend they are sure the prox- 



