Voi- XI] BERRY— FOSSIL CHITONS 403 



Callistochiton crassicastatus Pilsbry 

 " palmulatus Carpenter 



" var. mirabilis Pilsbry. [These 



both given as C. p. mirabilis in the 

 present paper] 

 Trachydermon dentiens Carpenter [=Mopalia acuta (Car- 

 penter) of the present paper] 

 Mopaliidcu sp. 



B. L. Clark ( :18, p. 191) records and figures an undeter- 

 mined chiton valve from the San Lorenzo Oligocene near Wal- 

 nut Creek, Contra Costa County, California. 



The most extensive published list of fossil chitons from any 

 part of the area under study is that of E. P. and E. M. Chace 

 ( :19, p. 42-43), based on determinations made by the present 

 writer on material which is part of that forming the subject of 

 this report. The exposure from which the material was ob- 

 tained has been termed by Mr. and Mrs. Chace, "The Chiton 

 Bed," and is situated at Point Fermin, Los Angeles County. 

 California. They list the following species : 



ToniccUa lincata (Wood) 

 Cyanoplax hartwegii (Carpenter) 



Nuttallina cf. fluxa (Carpenter) [=N. calif omica (Nut- 

 tall) of the present paper] 

 Mopalia ciliata (Sowerby) 

 lignosa (Gould) 

 " mnscosa (Gould) 

 Placiphorclla vclata Carpenter 

 Chcctopleitra gemmea Carpenter 

 Ischnochiton magdalencusis (Hinds) 



" coopcri Carpenter 



Callistochiton crassicostatus Pilsbry 

 " decoratus Carpenter 



This brings the total number of fossil species hitherto re- 

 corded from our area to 21, all from the Pleistocene and Plio- 

 cene, with an uncertain representative from the Oligocene. In 

 the present work the number is increased to 33 which are clearly 

 distinct, besides two or three uncertain ones. Of these one 

 only is of Oligocene age; a few are Pliocene: most are from 

 the Pleistocene formations. No chitons of any description ap- 



