PACIFIC FRESH WATER FISHES. 



2 49 



TABLE SHOWING THE VAEIATION IN THE NUMBER OF PLATES 



IN GASTEROSTEUS WILLIAMSONI—Cohtikvkv. 



The number at the head of each column indicates the number of plates. 



This table shows a complete gradation in the number 

 of plates from specimens wholly naked to those fully 

 plated. The specimens from the Santa Ana River are 

 almost invariably without any plates. About one -fourth 

 of those from the Santa Clara River in Ventura county 

 are without plates, the others having from one to four. 

 Into this stream flow the brooks of Williamson's Pass, 

 which is the type locality of Gasterosteus ■williamsoni. 



Proc. Cal. Acad. Sci., 2d Sek., Vol. VI. ( 19 ) June 23, 1896. 



