Vol. XII BERRY— FOSSIL CHITONS 4g3 



One would expect the shell from Point Fermin to he an im- 

 mature ferminicus, hut it is so different from its associated 

 specimens and so similar to recent shells that I refer it here. 



From the associated members of the genus this species as a 

 whole is remarkably distinct. The less highly modified inser- 

 tion teeth, the 1 1 more or less carinated rihs of the head valve, 

 the 9 similar ribs of the tail valve, and the delicate ribbing of 

 the central areas are among the more easily available distin- 

 guishing features. 



33. Callistochiton decoratus ferminicus Berry, new subspecies 

 (Plate XIV, figs. 7-8.) 



Diagnosis: Similar to the preceding subspecies, but larger, 

 much more elevated, with more strongly arcuate side slopes ; 

 sculpture of the central areas continuous over the jugum with- 

 out the interposition of a smooth area, the longitudinal riblets 

 Aery fine and numerous, 20-24 on a side. 



Type: An intermediate valve [1040] entered as Cat. No. 

 4571 of the author's collection. A paratvpe is Cat. No. 4572 

 [1095]. 



Type Locality: Chiton Bed, Lower San Pedro Pleistocene, 

 Point Fermin, California; E. P. and E. M. Chace, 1918: two 

 median valves. 



Description: (See diagnosis above.) 



Material Examined : No specimens other than the type, 

 paratvpe. and another specimen taken from the same exposure 

 by Chace and Berry in 1920 have been seen. 



Remarks: The Callistochiton decoratus complex is so 

 extraordinarily variable for a chiton, it is only with diffidence 

 that one adds a new name to the already overburdened list. 

 Nevertheless the differences among three of the fossil valves 

 from Point Fermin and all other fossil or recent specimens I 

 have seen are too patent to go without recognition. None of a 

 very extensive series of recent specimens before me approaches 

 ferminicus either in fineness of sculpture of the central areas, in 

 elevation, or in size. 



Although otherwise in fair condition, the type is too worn 

 within to show the characters of the articulamentum, and un- 

 fortunately the paratvpe is rather badly broken. 



The dimensions of the type are : Length, 4.+ ; diameter, 9.8 ; 

 height 4.6 mm. 



