Vol. XI] BERRY— FOSSIL CHITONS 405 



from any single geological horizon within our area, and so is 

 of hardly less consequence. 



The Stephens collection does not contain so many specimens 

 as the others, but these are representative of various important 

 formations in the vicinity of San Diego. 



The Arnold and Oldroyd collections are remarkably rich in 

 their representation of species, but the maximum value of much 

 of this material has been lost by inadequate station labeling. 

 Evidently, also, there has been some mixture of specimens. 

 However, the material is included in this report both for the 

 sake of completeness and because many of the specimens had 

 already been utilized for purposes of illustration before the 

 better ones came to hand. 



In the Arnold and Hannibal collection and that of the Cali- 

 fornia Academy of Sciences are specimens of the interesting 

 new chiton described from the Vancouver Island Oligocene. 

 The museum of the latter institution has also furnished speci- 

 mens from one of the Point Loma Pleistocene exposures. 



The University of California collection contains mainly re- 

 cent chitons, but some of these have been valuable for purposes 

 of comparison. 



Summary of Stations 

 oligocene 

 Sooke Formation: 



1. Sea cliff between mouths of Muir and Kirby creeks, 

 Vancouver Island, British Columbia (Harold Hannibal, N. P. 

 129; Cal. Acad. Sci. Loc. 231). 



It is through the kindness of Dr. B. L. Clark, who is en- 

 gaged in working up the fauna of this formation, that the single 

 chiton species obtained can be included here. It is 



Oligochiton lioplax Berry, new species 



San Lorenzo Formation: 



2. Walnut Creek, Contra Costa County, California (B. L. 



Clark). 



I have had no material from this horizon, but Clark ( :18, p. 

 191, pi. 14, f. 2) records and figures the valve of an unde- 

 termined chitonid species. Unfortunately the original speci- 



