Vol. XII 



BERRY— FOSSIL CHITONS 415 



Mopalia lignosa (Gould) 



" acuta (Carpenter) 

 ? Lepidochitona (initials (Gould) 

 Nuttallina calif ornica (Nuttall) 



All of these are no doubt from the Pleistocene, but whether 

 from the Lower or Upper Series it would serve no good pur- 

 pose to hazard a guess. 



The exact formation from which Cooper recorded Crypto- 

 chiton stelleri as of the Pleistocene of San Diego, and I sch no- 

 chiton magdalcnensis from the Pleistocene at Santa Barbara are 

 not known to me. 



It is strange that no chitons have been reported from the 

 rich Pleistocene deposit on the beach behind the bathhouse at 

 Santa Barbara. I did not find any during my exploration of 

 these beds in 1903, although they must occur there. 



Relative Abundance of Species 



Chiton valves do not seem to be very common in most 

 horizons and are really abundant only in four of those ex- 

 amined,— the Upper San Pedro Beds of Long Wharf Canyon, 

 the Lower San Pedro at Nob Hill Cut, and the two Point 

 Fermin exposures, especially that known as the "Chiton Bed." 

 Out of a total of 1040 valves which constitute the principal 

 subject matter of this paper, over one-half are the result of our 

 few trips to the "Chiton Bed", and the overhauling of Dr. 

 Clark's material from Long Wharf Canyon. 



The most abundant species as fossils are not by any means 

 always those most commonly taken in present day collecting. 

 No less than 203 of the fossil valves are Callisto chiton palmu- 

 latits mirabilis, and another Callisto chit on (crassicostatus) 

 stands second in point of abundance with 131, largely the con- 

 sequence in both instances of their plentiful occurrence at Long 

 Wharf Canyon. The only other species of which 25 or more 

 specimens have come to hand are Nuttallina calif ornica (161 ), 

 Lepidochitona dentiens (63), Mopalia muscosa (80), Ischno- 

 chiton magdalcnensis (92), Mopalia acuta (49), Mopalia 

 ciliata (47), Ischnochiton acrior (31), and Ischnochiton 

 cooperi (26). 



