CHAPTER XXIX. 



REPORT ON THE PALAEONTOLOGY OF THE SURVEY. 



BY T. A. CONRAD. 



Dear Sir : Accompanying this is the description of the fossils collected by you in southern 

 California. 



In the Proceedings of the Academy of Natural Sciences for 1855, page 441, I have remarked 

 that the Miocene of Santa Barbara contains a group of shells more analogous to the fossils of 

 tne Atlantic slope than to the existing shells of California ; but it is evident, from the specimens 

 in your collection, that there must be subdivisions in those tertiary deposits of California which 

 range between the Eocene and Pleiocene periods, for the group of the Estrella valley and Santa 

 Inez (Barbara) mountains does not appear to contain one species, even, analogous to any in the 

 Santa Barbara beds, and, on the contrary, some of them remind us of the existing Pacific fauna. 

 Thus, Dosinia Alfa is closely allied to D Simplex, Hinnites crassa related to Rinnites giganfea. 

 Pachydesma and Crytomya are existing California genera, represented in the Miocene, and 

 which do not occur in the Atlantic. I think it probable that the Estrella group may prove to 

 be of later origin than that of Santa Barbara. There is another at San Diego, of which I have 

 seen but a few specimens, and cannot yet determine its relation to the other groups. In referring 

 these fossils to the Miocene group, it is not with the understanding that they are exactly parallel 

 with European or even Virginian Miocene strata, but that they are unquestionably situated 

 between the Eocene and newer Pliocene, containing no species analogous to the former, which is 

 admirably characterized in California by its general forms, and even by a few well known Clai- 

 borne species. Like the Miocene of Virginia, the Estrella group is characterized by large and 

 even comparatively gigantic species of Pectinidae, so unlike any living on the coasts of California 

 or the Atlantic States. It would seem that this family then reached their maximum of devel- 

 opment and the genus Pallium was first introduced, and of far larger size than any which now 

 exist. It is worthy of remark that the generic character is developed on a far grander scale 

 than appears in subsequent epochs, the prominent teeth and thick hinge reminding us of the 

 genus Spondylus. 



Every new collection of Miocene fossils shows more clearly the connection between some of the 

 tertiary strata of California and those of Virginia. The species in the present collection are 

 far more interesting than any others of the same formation on the Pacific slope which I have 

 yet seen. It does not appear that this group of fossils has any living representative in the 

 present fauna of the Pacific coast, but several of them approximate to extinct Virginia species ; 

 and I am not sure that the large Pecten magnolia, herein described, is not identical with the 

 Virginia species P. Jeffersonius. I think it may safely be assumed that the San Raphael hills, 

 Santa Inez mountains, and Estrella valley, contain strata which are parallel to the Miocene sands 

 and clays of the James and York rivers, in Virginia. No doubt there are groups of different geo- 

 logical age, as the species vary greatly in different localities ; but in your collection I find not one 

 Eocene species, and none more recent than the Miocene, except the few shells collected from the 



