Of the 107 species of fossils found in Division B, 44 are found at Clayton, 67 at Tejon, 54 at Martinez, 22 at San Diego, 18 near Griswold’s, and 7 near New Idria. It is not intended to be understood that these are all of the species found at these localities; but that, up to the present time, these are all that have been identified or described. Future work will undoubtedly change the above figures.
Of the species found at the above localities, 50 are peculiar to one or another locality; 29 are found at two localities only, 14 at three localities, and 14 at four localities or more.
Taking the three typical localities, Martinez, Clayton and Tejon, 21 species are common to Martinez and Clayton, 30 to Martinez and Tejon, 25 to Clayton and Tejon, and 20 are found at all three localities.
Now, having given what I believe ought to be considered proof conclusive to any candid mind in support of my first proposition, I shall endeavor to establish the second.
It will be seen that 16 species, found in the upper member, also extend into the older group, Division A. In addition to this, at the locality near Lower Lake Village, Lake County, besides several species encountered for the first time, I found 15 species in the same bed, within a superficial area of two feet. Of these, 3 were previously known to be common to the upper and lower division. Besides these 3, 7 of them were common to this locality, and localities of Division B, and the remaining 5 were, before this discovery, considered peculiar to the lower member. One of these 5 is found in the Mississippi Valley, in the “Ripley Group,” and another belongs to a peculiarly Cretaceous genus.
As to the species found at the several typical localities, independent of each other, and which would serve to show their individual relations to the older formation without corroborative evidence, Clayton has 10 species in common with Division A, Tejon has 7, and Martinez 11. With the Lower Lake bed, Clayton has 5 species in common, Tejon 5, and Martinez 6.
In glancing over Mr. Conrad’s “check list,” I find that out of the 107 species found in his “Older Eocene of California,” he has only included 74 in his enumeration. He has omitted Callianassa Stimpsonii, Ammonites n. s., Nautilus Texanus, Cylichna costata, Mactra Ashburnerii, Cucullæa Mathewsonii, Nucula truncata, and Leda protexta; eight species, which I mentioned in the Journal of Conchology, (Vol. 2, p. 88) as being found in common in the two members of the Cal. cretaceous, stating distinctly the localities in which they had been found. At the same time he includes five other species, from the same list, in his Eocene catalogue. Whether this be carelessness, or an unfair avoidance of a difficulty, I leave to others to decide. It is far easier to ignore such a difficulty than it is to explain it away.
In regard to the distribution of the genera and species in this and the associated rocks. All of the species are peculiar to this group, or to this and underlying rocks; not one has been found associated either with living forms, or with species known to occur in the recognized Tertiaries of California. Five of the genera are peculiar to the Secondary. An Ammonite ranges entirely through the group to the top of the highest fossiliferous strata. The genera Perissolax, Gyrodes, Margaritella, and the sub-genus Anchura, of the genus Aporrhais, are all recognized as strictly characteristic of the Cretaceous; so much so, that the presence of a single undoubted representative of either of these genera would be strong presumptive evidence of the Cretaceous age of any rocks in which it might be found. On the other hand, the presence of such genera as those in the list given below, would point to a very modern era in the Cretaceous, to say the least.
It must be borne in mind that we have much to learn yet in palæontology, especially in the matter of the vertical range of genera. Every year we find genera, nay, whole families, extending themselves beyond what had been fixed by previous authors as their limits. A few years ago, the presence of mammalian remains was considered characteristic of the Tertiaries. Now we know of Marsupials in the Trias, and who dare say that we cannot find mammals in palæozoic rocks? I therefore maintain, that though we have here such genera as Aturia, Typhis, Cordiera, Pseudoliva, Nassa, Mitra, Ficus, Morio, Cerithiopsis, Cypræa and Galerus, still, the only inference that can be drawn is, that the group is on or near the verge of the formation, a sort of prophetic member, presaging by some of its genera the formations to come, but indissolubly bound by specific ties with the eras preceding.
[29] This species was referred by inadvertence to Div. B. instead of A. This is the first time it has been found beyond the limits of the lower member.