DISCUSSION. 



Dr. G. M. Dawson : Further evidence of the great north-and-south range 

 of the earlier Cretaceous beds has been brought forward by Mr. R. G. Mc- 

 Connell, who recently discovered Aucella-hearlng beds as far north as Porcu- 

 pine river, within the arctic circle. There are some grounds for preferring 

 the term early (or earlier) Cretaceous for the beds in question to the term 

 lower Cretaceous. The strata appear to represent in at least a general way 

 the middle Cretaceous of Europe ; and it scarcely admits of doubt that fossils 

 referable to still lower stages will eventually be found on the Pacific coast 

 in the great mass of Cretaceous rocks as yet only partially examined. 



Mr. J. S. Diller: In Tehama county, California, where the contact be- 

 tween the Knoxville and Horsetown beds is w^ell exposed, their relation, 

 hitherto based wholly upon paleontologic evidence, can be studied to great 

 advantage. The region is just north of the 40th parallel, extending from 

 Tehama into Shasta county, and lies between the localities of California and 

 Oregon referred to by Mr. Becker. On Elder creek, at the eastern base of 

 the Coast range, the unaltered fossiliferous Cretaceous strata have an apparent 

 thickness of nearly 30,000 feet.* The whole series, including both the Chico 

 and Shasta groups, dips eastward away from the Coast range with remark- 

 able uniformity and appears to be one continuous series of sediments, from 

 top to bottom, without evident physical break. In the lower 19,900 feet, the 

 only fossil found is Aucella. The sedimentary rocks are limited below by 

 serpentines, resulting from the alteration of peridotitic eruptives, such as 

 form a considerable portion of the Coast range. In the upper 3,900 feet, 

 Chico fossils occur abundantly; while in the intermediate 6,100 feet, Horse- 

 town forms have been found. They are best exposed in the Bald hills, be- 

 tween Paskenta and Lowrey's, where Aucella occurs abundantly in the basal 

 portion, associated with Ammonites batesii, Trsisk ; A. ramosus, Meek; A. 

 trasJcii (?), Gabb ; Ancyloceras percostatus, Gabb ; Bhynchonella, sp. nov. ; 

 Siliqua, sp. (?) These strata have been traced northward about 40 miles to 

 the original Horsetown beds on the North fork of Cottonwood creek, where 

 the first four fossils named have been found either by myself or other ob- 

 servers.f It is especially noteworthy th?it Aucella, although diligently sought 

 for, has not been found in that region north of Elder creek, t 



* Am. Journ. Sci., 3d series, vol. XL, 1890, p. 476. During the field season of 1888-89, Cretaceous 

 fossils were collected in that region from 79 localities, of which '24 yielded forms belonging to the 

 Shasta group. They were all identified by Dr. C. A. White and T. W. Stanton. 



fCf. Geol. Survey of Cal., Palaeontology, vol. II, 1-69, pp. 210, 211, 213. 



t While the ^uceMa beds form, with the Horsetown beds, a continuous vertical series they are 

 of very unequal horizontal distribution. The Horsetown beds lap far over to the northward upon 

 the older metamorphic rocks beyond the yl?tceWa beds, in much the same way as the Horsetown 

 beds are themselves overlapped by those of the Chico group. North of Riddles, in Oregon, on the 

 South fork of the Umqua, about two miles below the mouth of Cow creek, a great thickness of 

 strata in which Aucella only has been found are well exposed. Downward they pass apparently by 



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