408 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



This exposure has received very full treatment at the hands 

 of Arnold ( :03, p. 18-21, 35-47). The single chiton re- 

 corded is : 



Cryptochiton stellcri (Middendorff) 



I have seen no chiton material definitely known to be from 

 this horizon, but it is possible that a portion of the miscel- 

 laneous material in the Arnold and Oldroyd collections came 

 originally from these beds. 



9. "The Chiton Bed," near the pavilion, Point Fermin, Los 

 Angeles County, California (E. P. Chace, E. M. Chace and 

 S. S. Berry). (Plate XVI). 



This interesting exposure is the one which has been recently 

 described by Mr. and Mrs. Chace ( :19, p. 41-43). So unusual 

 is the deposit from the large number of chiton valves contained 

 in it that they have termed it "The Chiton Bed," a usage so 

 convenient as a brief means of distinguishing it from neighbor- 

 ing deposits of the same formation that I retain it in the fol- 

 lowing pages. Besides giving a considerable faunal list, their 

 paper described the field relations of the exposure as follows : 



It is situated a few yards west of the western boundary of the picnic 

 grounds around Peck's Pavilion, and hardly more than ten feet below the 

 upper edge of the bluff. Directly below the rather sandy topsoil a thin 

 layer of red-brown sandstone is exposed, then comes the fossil-bearing 

 stratum : a gray sand, in some places so hard as to offer considerable re- 

 sistance to the caseknife, in others weathered to a loose, trickly deposit. 

 Immediately below this is another layer of the red-brown previously seen. 

 Owing to the conformation of the bluff I am unable to say what lies 

 beneath the second red layer. There are numerous small stones in the 

 fossiliferous layer, some of them apparently chalcedony, others our com- 

 mon white quartz, still others are fragments of a dark shale. These stones 

 have probably prevented a previous report of this exposure, as at a little 

 distance the shells are thoroughly masked by these bits of rock. It is an 

 odd fact that although the gray sandstone layer continues, apparently un- 

 changed, both to the east and west of the ten-foot section in which we 

 have worked, we were unable to find any shells except in that small space." 



Later in their paper these authors express some doubt as to 

 the geologic age of these strata, but it seems to me that the 

 evidence of the lithology, of the fauna in general, and espe- 

 cially of the chitons themselves, is conclusive that they should 

 be correlated with the Lower San Pedro. The latter in its 

 characteristic form is likewise a rather hard gray sandstone, 

 and the aspect of the embedded fauna, as here, is quite dis- 

 tinctly northern. As will be noticed from the following list, the 



