852 PROCEEDINGS OF THE NATIONAL MUSEUM. VOL. XXXIV. 
The following species have been found in the Santa Margarita for- 
mation within the quadrangle: 
List of Santa Margarita, upper Miocene, fossils from the Santa Cruz quadrangle. 
ECHINOIDEA. 
Astrodapsis antiselli Conrad. 
OPHIUROIDEA. 
Amphiura sanctecrucis Arnold, 
PELECYPODA. 
Pecten crassicardo Conrad. 
TRANSITIONAL MIOCENE-PLIOCENE. 
Purisima formation.—A large portion of the Santa Cruz quad- 
rangle is occupied by an apparently continuous series of sediments 
composed of heavy conglomerates, sandstones, breccias, impure soft 
mud shales, and white diatomaceous shale like the Monterey shale. 
The formation as here defined attains a maximum thickness of be- 
between 5,000 and 8,000 feet, and includes a thick mass of sediments 
representing upper Miocene and much of Pliocene time. They appear 
to be conformable, and no area was found where they could be con- 
veniently subdivided. 
~The Purisima beds lie unconformably upon the Vaqueros sand- 
stone and are usually unconformable above the Monterey shale; up- 
ward they grade into beds having a fauna similar to that of the 
Merced formation. The upper limit of the Purisima may be defined 
as the base of the Merced, as exposed in the type section of Merced 
on Seven-mile Beach south of San Francisco and north of the Santa 
Cruz quadrangle. 
Overlying the Miocene basalt in the region south and southwest of 
Stanford University are some fossiliferous beds which have been 
mapped with the Purisima but which are probably older than any 
of the Purisima in the type region. ~ 
The fauna yielded by these beds, which are believed to be the 
equivalent of what Merriam has called the ‘“ Contra Costa County 
Miocene,” is as follows: 
List of fossils from the lower part of the Upper Miocene of the Santa Cruz 
quadrangle. 
PELECYPODA,. 
Arca (cf.) obispoana Conrad. Pecten andersoni Arnold. 
Arca canalis Conrad. Periploma sanctwcrucis, new species. 
Chione (cf.) temblorensis Anderson. Saxridomus (cf.) gibbosus Gabb. 
Chione mathewsonii Gabb. Solen sicarius Gould. 
Dosinia mathewsonii Gabb. Spisula (cf.) californica Conrad. 
Dosinia ponderosa Gray. Tapes (cf.) staleyi Gabb. 
Leda taphira Dall. Yoldia supramontereyensis, new spe- 
Panopea generosa Gould. cies. 
Phacoides acutilineatus Conrad. 
