Vol. XIJ 



BERRY— FOSSIL CHITONS 



459 



Indian middens: La Push, Washington (Reagan) ; near 

 Cypress Point, Monterey County, California; San Nicolas 

 Island. California ( !). 



Living: Northern Japan, Sakhalin, Kuril Islands, Kam- 

 tschatka. and Bering Sea, to Monterey Bay and the Santa Bar- 

 bara Islands, California. 



Material Examined : 



Remarks: This characteristically boreal Pacific species is 

 not common in any of the formations where it has been reported 

 to occur. The large size and massive formation of the valves, 

 however, render it a difficult species to overlook, and hence we 

 find that it has been reported from more horizons in the area 

 studied than any other chiton. Its occurrence in the Point 

 Loma Pleistocene in the same exposure as the decidedly south- 

 ern Ischnochiton acrior came as a distinct surprise. 



I have been unable to differentiate any of the fossil shells 

 from the recent ones morphologically in any way. One of the 

 fossil specimens, however, a head valve in the collection of the 

 California Academy of Sciences [517], is remarkable for the 

 fact that the calloused inner layer of the shell has been entirely 

 delaminated, exposing the internal and usually invisible radial 

 grooves and concentric growth lines with exquisite perfection 

 (PI. VI, f. 10). Of the radial grooves, the six posterior radiate 

 toward, and as usual are in correspondence with, the insertion 

 slits. Another pair of grooves diverges anteriorly on each side 

 of the sinus. Caliper measurements of this specimen are : Max. 

 long. 27.2, max. diam. 32.1, alt. 10.0 mm. 



