LORQUINIA 
Occasional Papers at the L,orquin Natural History Club of the Southwest Museum 
Published by the Lorquin Natural History Club. 
January VOL • 2 Los Anja^eles, California. ^J0«6 1919 
AN UNREPORTED EXPOSURE OF THE SAN PEDRO 
PLEISTOCENE 
E. P. and E. M. Chace 
Sixteen years ago, when Dr. Ralph Arnold published his work on 
the Paleontology and Stratigraphy of the Marine Pliocene and Pleisto- 
cene of San Pedro, California, he made the remark that "we have in 
the California deposits the greatest development of the marine Ple- 
istocene in the world." Some of the exposures on which he based this 
statement have since been obliterated by improvements in and around 
San Pedro, but others that were apparently unknown to him are still 
being reported. Among the latter is one to which we have given the 
name, "The Chiton 13ed, Pt. Firmin." 
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 fossiPbearing stratum : a gray sand, in some places so 
hard as to offer considerable resistance to the Taseknife, in others 
weathered to a loose, trickly deposit. Immediately below this is 
another layer of the red-brown previously seen. Owing to the con- 
formation 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 common 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 
unchanged, 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. 
We have visited the exposure three times, and from the material 
collected have identified the following species, with two exceptions : 
IVillkunia vernalis, Ainphissa varicgata, which Dr. Dall of the U. S. 
National Museum has kindly identified for us, and the chitons, which 
