20 H. Doc. 129. 



61. P. CATILLIFORNIS, Conrad, pi. viii, fig. 83. Orbicular plano- 

 convex, with radiating stride and distinct rounded ribs; ears equal. 



Locality. Ocoya creek. W. P. Slake. 



This large Pecten has such a general resemblance to P. Madisonius, 

 Say, of the Virginia Miocene, that I have no doubt it existed at the 

 same period, or at least after the Eocene. There is none such now 

 living on the coast of California, and none in the Eocene, of this group 

 of large Pectens, which occur almost everywhere in the Miocene 

 deposits of the Atlantic slope. 



In addition to the above described species, there are many specimens 

 and drawings in which the specific characters are not preserved with 

 sufficient distinctness for description. Among these are individuals 

 of the genera Cardium? or Area, Solen, Dosinia and Venus. 



REMARKS IN CONCLUSION. 



BT W. P. BLAKE. 



From this report by Mr. Conrad, we find that in the collection of 

 61 determinable species, 55 are new and are now described for the first 

 time. Of these, 10 are from one locality at the southern extremity of 

 the Tulare valley, at the entrance to the pass called the Canada de 

 las Uvas. They are considered to be of the age of the Eocene by 

 Mr. Conrad, who notes the similarity between three of the species and 

 those of the Alabama Eocene deposits at Claiborne. (See Mr. Con- 

 rad's letter.) These fossils were imbedded in a boulder of compact 

 sandstone that had been washed out of the ravine of the pass by floods. 

 The rock was not found in situ at that point, but a few miles to the 

 westward a similar rock occurs in place, and is replete with fossils. 

 These are believed to be the first fossils of Eocene age that have been 

 procured from the Pacific slope of the United States. 



The sedimentary formations of Ocoya creek (Pose creek) are con- 

 sidered to be of the age of the Miocene, and twelve new species from 

 that locality are described. There were numerous specimens of other 

 species in the collection, which were not sufficiently characteristic for 

 determination, but which are probably new. Eight new species of 

 Miocene shells are described from San Diego, and ten of a more recent 

 formation from San Pedro. These last occur in a bank fronting the 

 bay, and which is partly undermined by the surf. This bank is filled 

 with shells, and the principal stratum is about 30 feet above tide. 



The fossils from the sandstones along Carrizo creek, near the point 

 where it spreads out and is lost in the desert, are all new and of Mio- 

 cene age. 



The Miocene formation appears, therefore, to flank the Peninsula 

 Sierra on both sides in the latitude of San Diego, and to underlie the 

 alluvial deposits or delta of the Colorado. There is a remarkable dif- 

 ference in the appearance of the fossils on the east and west sides of 

 this chain. Those on the desert side form a stratum four or five feet 

 thick of shells alone, consisting almost wholly of the genera Ostrea, 



