Ajg CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



30. Ischnochiton (Lepidozona) sanctaemonicae Berry, 



new species 



(Plate XII, figs. 1-9.) 



1917. Ischnochiton clathratus Chace, Lorquinia, v. 2, p. 30. 



not Chiton clathratus Reeve 1847 (recorded from 



Pleistocene of Santa Monica, Cal.). 



Diagnosis: Valves small, thin, elevated, carinate; side 

 slopes nearly straight; lateral areas elevated, divided into 4-5 

 low, distinct, radial ribs, with narrower, coarsely granular in- 

 terspaces, the sutural margin weakly dentate; head valve sim- 

 ilarly sculptured, the ribs 32-47 in number ; posterior area of tail 

 valve similarly sculptured with about 25 ribs, obsolete toward 

 the mucro; central areas on each side with 25-28, fine, more 

 or less nodulose, longitudinal riblets, with abrupt, rather wider, 

 deeply channeled interspaces, decussated by coarse, transverse 

 threadings nearly as strong as the longitudinal ribs ; mucro of 

 tail valve low, median; sutural laminae low, wide, connected 

 across the shallow sinus by a short toothed plate ; teeth stout, 

 somewhat projecting; eaves rough but not truly spongy; slits 

 11, 1-1, 10, with conspicuous pore lines leading into them. 



Type: An intermediate valve [883] entered as Cat. No. 

 3992 of the author's collection. A paratype is deposited in the 

 collection of the California Academy of Sciences and there is 

 one in the private collection of Dr. F. C. Clark. 



Type Locality: Upper San Pedro Pleistocene of Long- 

 Wharf Canyon, Santa Monica, California ; Dr. F. C. Clark ; 3 

 head, 9 median, 1 tail valves. 



Range: Unknown except type locality as given above. 



Material Examined: 



