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 he 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, Dosiuia Alta is closely allied to D Simplex , Rinnites crassa related to Rinnites gigantea. 
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 
he 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 aroexactly parallel 
with European or even Virginian Miocene strata, hut 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 ai.d 
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, hut 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 he 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 ; hut in your collection I find not one 
Eocene species, and none more recent than the Miocene, except the few shells collected from the 
