In consideration of the scanty material, it is by no means surprising that Mr. Conrad should have made the determination that he did. The fossils of this locality, and, in fact, of this member of our Californian rocks, have a marked Tertiary aspect. This holds good, both as applied to the appearance of the specimens and also to the grouping of the genera. Mr. Conrad’s reference of these fossils to an Eocene age was perfectly justified by the light that he then possessed. Any other palæontologist, with the same specimens, would no doubt have done as he did. But I propose to prove that, after having studied this formation for five years, both in the field and in the closet—both palæontologically and stratigraphically—after having traced it upwards of four hundred miles, and after having collected fossils from it at a dozen localities, I, on the other hand, am perfectly justified in pronouncing it most unequivocally Cretaceous.
It is, to use a mild term, rather surprising that Mr. Blake, from whom Mr. Conrad obtained his material, should not have collected more specimens. According to his report, Mr. Blake reached the depôt camp at Tejon, on the third of September, 1853, and did not leave that vicinity until October 10th. During that time he traversed the distance between Tejon and the Cañada de las Uvas, four times. I am familiar with every foot of the ground on which he camped or on which he travelled; and I speak from personal observation, when I say that in going from one point to the other he could not avoid passing thousands of boulders and pebbles, full of fossils, similar to the single one sent to Mr. Conrad. In riding from the Ranch house of Tejon to Fort Tejon, on Mr. Blake’s trail, Professor Brewer and myself collected upward of forty species of mollusca in less than one hour, and without diverging ten feet from our route!
The Californian Cretaceous formation is easily separable into two main divisions. The older of these, designated in the Report as “Division A,” is the equivalent of the upper portions, Nos. 4 and 5, of Meek and Hayden’s section in Nebraska, and the later beds of New Jersey and the Gulf States. It is possible that this group may be separated hereafter into two sub-groups; but that has no bearing on the question at issue. The upper or more modern member, found overlying the lower one conformably in various places, as about Monte Diablo and at Martinez, has no apparent equivalent in America. It is probably, however, the American representative of the Maestricht beds, the ‘Danien’ of French authors. It is not a transition from Cretaceous to Tertiary, but is the most modern member of the former formation.
It has many points in common with the Maestricht beds of Europe. It contains but a single species, so far as known, of the complex-chambered group of Cephalopods. A solitary ammonite, represented by half a dozen specimens, has been found by myself, in place, even to the very top of the formation.
Of 280 species of fossils recognized and named in the Californian Cretaceous rocks, 107 are found in this upper member. Of these, 84 are peculiar, and 23 are found in common between undoubted members of this group and undoubted members of the older group. Besides this, I was fortunate enough to discover a locality near Clear Lake, this fall, where, within a space of two feet, I found an admixture of upper and lower forms, proving the existence of a transitionary bed or perhaps group of beds. The following table will exhibit at a glance the grouping of species at each of the principal localities; showing at the same time which species are found in the intermediate deposit, and which exist in common in both the upper and lower divisions. The various localities are designated by letters, as follows: M, Martinez; C, Clayton to Marsh’s; T, vicinity of Fort Tejon; G, a locality 10 miles west of Griswold’s near New Idria; I, New Idria; D, San Diego; LL, Lower Lake Village, 1 mile S.E. of the town.
TABLE OF SUBDIVISIONS OF CRETACEOUS FORMATION.
| Upper Division. | Intermediate Beds. | Lower Division, and Remarks. | |
|---|---|---|---|
| Callianassa Stimpsonii | C. T. | Chico. | |
| Aturia Mathewsonii | M. C. T. | Martinez. | |
| Nautilus Texanus | C. | Shasta Co. | |
| Ammonites, n.s. | C. M. | Curry’s; Benicia; Martinez. | |
| Typhis antiquus | M. T. | ||
| Fusus Martinez | M. T. | ||
| F. Mathewsonii | M. C. | Curry’s. | |
| F. Diaboli | C. | ||
| F. aratus | M. | ||
| F. Californicus | C. T. | LL. | |
| Hemifusus Hornii | T. | ||
| H. Cooperii | C. D. | ||
| H. Remondii | M. C. T. G. | ||
| ? Neptunea supraplicata | C. D. | ||
| N. gracilis | M. | ||
| Perissolax brevirostris | LL | Many localities. | |
| P. Blakei | M. C. T. | ||
| Turris Claytonensis | C. T. | ||
| Turris raricostata | C. | (varicostata by error in Rep.) | |
| Cordiera microptygma | T. | ||
| Tritonium Hornii | C. T. | ||
| T. Diegoensis | D. | ||
| T. paucivaricatum | T. | ||
| T. Whitneyi | T. D. | ||
| Buccinum liratum | M. | LL | |
| Nassa cretacea | M. T. G. | ||
| Pseudoliva lineata | M. | ||
| Pseudoliva volutæformis | T. | ||
| Olivella Mathewsonii | M. T. G. C. | ||
| Ancillaria elongata | C. D. | ||
| Fasciolaria læviuscula | C. | LL | |
| F. sinuata | T. D. | ||
| F. Io | T. | ||
| Mitra cretacea | M. | ||
| Whitneya ficus | T. | ||
| Ficus mamillatus | T. | ||
| Natica Uvasana | T. | ||
| Lunatia Shumardiana | LL | Martinez and elsewhere.[29] | |
| L. Hornii | T. | ||
| L. nuciformis | C. T. (D.?) | ||
| Gyrodes expansa | LL | Almost everywhere. | |
| Neverita secta | T. | ||
| N. n.s. | G. I. | ||
| Naticina obliqua | M. T. | ||
| Amauropsis alveata | M. C. T. G. D. | LL | Curry’s; S. of Mt. Diablo. |
| Morio tuberculatus | M. T. C. G. D. | ||
| Scalaria (Opalia) Mathewsonii | M. | ||
| Niso polita | M. T. | ||
| Cerithiopsis alternata | M. C. | ||
| Architectonica cognata | M. C. T. | ||
| A. Hornii | T. | ||
| Margaritella crenulata | D. | ||
| Conus Remondii | M. C. T. D. | ||
| C. Hornii | T. | ||
| C. sinuatus | T. | ||
| Rimella canalifera | M. T. | ||
| R. simplex | C. D. | ||
| Aporrhais angulata | M. | ||
| Cypræa Bayerquei | M. C. | ||
| Turitella Uvasana | M. C. T. G. | ||
| T. Saffordii | LL | M. and Solano Co. | |
| T. infragranulata | M. | ||
| Galerus excentricus | M. C. T. D. I. | LL | |
| Spirocrypta pileum | T. I. | LL | |
| Gadus pusillus | M. T. | ||
| Dentalium Cooperii | M. D. | Curry’s; S. of Mt. Diablo. | |
| D. stramineum | M. D. | Curry’s; S. of Mt. Diablo. | |
| Bulla Hornii | T. | ||
| Cylichna costata | M. C. T. D. | M., Texas Flat, and many other localities. | |
| Megistostoma striata | M. | ||
| Martesia clausa | G. | Pence’s, Texas Flat, etc. | |
| Solen parallelus | M. C. T. | ||
| Solena Diegoensis | D. | ||
| Corbula Hornii | T. | ||
| C. parilis | G. M. D. | ||
| Neæra dolabræformis | M. | ||
| Mactra Ashburnerii | M. C. T. | Nearly everywhere in both Divisions. | |
| Gari texta | M. | ||
| Tellina longa | M. C. T. | ||
| Tellina Remondii | C. T. | ||
| T. Hoffmanniana | G. | M., Pence’s, and elsewhere. | |
| T. Hornii | T. | ||
| T. Californica | C. T. | ||
| Meretrix Uvasana | M. C. T. I. G. D. | ||
| M. Hornii | T. | ||
| M. ovalis | T. | ||
| Dosinia elevata | T. | ||
| D. gyrata | M. C. T. G. | ||
| Tapes Conradiana | G. M. T. | LL | |
| T. quadrata | M. T. | ||
| Cardium Cooperii | M. T. D. | ||
| C. Brewerii | M. C. T. G. | ||
| Cardita Hornii | M. C. T. I. G. | ||
| Lucina cumulata | T. | ||
| L. cretacea | C. | ||
| Mysia polita | M. C. I. | ||
| Crassatella grandis | M. T. | LL | |
| C. Uvasana | T. | ||
| Mytilus ascia | T. | ||
| Modiola ornata | M. C. T. I. | ||
| Septifer dichotomus | T. | ||
| Crenella concentrica | M. | ||
| Avicula pellucida | M. G. | LL | S. Louis Gonzaga. |
| Arca Hornii | T. | ||
| Cucullæa Mathewsonii | C. | LL | M. |
| Barbatia Morsei | D. | ||
| Axinæa sagittata | M. T. G. | ||
| A. Veatchii | LL | M., Tuscan Springs, etc. | |
| Nucula (Acila) truncata | M. T. | Everywhere. | |
| Leda protexta | M. C. T. G. | M. | |
| Placunanomia inornata | D. | ||
| Flabellum Remondianum | C. |
On studying the foregoing table, the following deductions present themselves: 1st, that the rocks of the upper division, at the various localities quoted, are all of the same geological age; and 2d, that they are intimately connected with the older groups by a passage of nearly a fifth of all the contained species of fossils from this, either into the intermediate beds, or into the lower group itself.
In anticipation of a possible objection that may be raised here, it will probably be as well, before going further, to state that in the Division B, there has been no confounding of two groups. The same grouping of species extends to the extreme upper limits of the fossiliferous rocks, which are everywhere overlain by an immense deposit of non-fossiliferous sandstones. Another objection, which has already been raised, that the acknowledged Cretaceous fossils have become mixed with more modern species by the breaking up and re-cementing of an older formation, I shall not even attempt to refute. Had such been the case, I would ere this, in common honesty, have acknowledged it.
In support of the two conclusions arrived at above, we have the following synopsis of the table: