Vol. XI] BERRY— FOSSIL CHITONS 411 



southern. In many respects the association appears more or 

 less transitional between the Lower San Pedro Series and the 

 Upper, so perhaps is an older deposition than the typical 

 Upper San Pedro. It is the only supposedly Upper San Pedro 

 horizon in which Ischnochiton coopcri has been found. Pos- 

 sibly there has been a confusion of horizons, and both Upper 

 and Lower are really present here. I have accordingly treated 

 it as Lower San Pedro in my table. Further chiton material 

 from this locality is badly needed and might throw valuable 

 light on the relationships involved. Ashley's record of Ischno- 

 chiton rcgularis ('95, p. 343), from a supposedly Pliocene ex- 

 posure which Arnold ( :03, p. 24) identifies with the present 

 one, also requires confirmation. 



Upper San Pedro Series: 



13. Lumber yard, San Pedro, California (Arnold). 



This is the type locality of the Upper San Pedro Series 

 as described by Arnold. He records an extensive fauna ( :03, 

 p. 27-29, 35-47), but only two chitons are included : 



Mopalia ciliata (Sowerby) [=muscosa (Gould) 'of the 



present paper] 

 Ischnochiton rcgularis (Carpenter) 



I have had no material known with certainty to be from 

 this horizon. The specimens upon which Arnold based the 

 determinations cited appear to have been lost and attempts to 

 trace them have met with no success. 



14. Signal (or Los Cerritos) Hill, Long Beach, California 



(Oldroyd). 



Accounts of the stratigraphic relations and fauna of the 

 Pleistocene of Los Cerritos Hill have been published by Arnold 

 ( :03, p. 30-32, 35-47), who lists no chitons, and by Oldroyd 

 ( :14, p. 81), who records one, ■-..•:■•■> 



Ischnochiton conspicuus Carpenter 



The further material afforded by the Oldroyd collection 

 contains in addition to this species three others, . <; , _ . 



Mopalia acuta (Carpenter) 



Ischnochiton sp. 



Callistochiton palmulatus mirabilis Pilsbry 



