204 G. F. BECKER — EARLY CRETACEOUS OF CALIFORNIA. 



southern Oregon resemble those of the Knoxville group. The gently undu- 

 lating un metamorphosed Miocene sandstones, which are abundant along the 

 Willamette valley, unquestionably rest unconformably upon the plicated, 

 highly disturbed and metamorphosed strata near Roseburg, and there is 

 every reason to suppose these absolutely equivalent to the partially meta- 

 morphosed beds at Kiddles. Just so, in California, the Miocene of the Coast 

 ranges lies in broad, flowing curves upon the sharply folded or utterly 

 crushed masses of the Knoxville series. 



There is no indication of any lack of conformity within the fossiliferous 

 series. On the contrary, the various exposures, taken together, appear to 

 show that from the conglomerates to the limestones the layers of rock were 

 laid down without intervening disturbance. This observation is borne out 

 by the distribution of the fossils; for, while the entire list cannot'be collected 

 at a single point, a given locality will contain two or more species also found 

 at a lower horizon, as well as others met with at a higher stratigraphical level. 

 The entire area over which fossils occur, and in which there is no indication 

 of a stratigraphical break, is about three miles wide and five miles long. 



Fossils from Riddles. — In the collections made at Riddles by Mr. Brown 

 and myself, Dr. White has determined a few very significant fossils. These 

 are : 



Aucella concentrlca, Fischer ; 



Ammonites batesil, Trask ; 

 " trashli, Gabb ; 



Pecten opercidlformis, Gabb ; 



Pleuromya laevigata, Whiteaves ; 



Cardium (^Protocardium) translucidum, Gabb; 



Belemniies impressus, Gabb ; 



Area breweriana, Gabb. 



Of these fossils the Aucella is much the most plentiful, as it also is in the 

 Knoxville beds of California and in the gold-bearing slates of Mariposa 

 county. The two species of Ammonites are found in the Horsetown beds, and 

 are regarded as particularly characteristic of that horizon. The Pleuromya 

 and the Cardium have also been found rather abundantly at Horsetown by 

 Messrs. Diller and White and by myself, and the Belemnites, which is, of 

 course, a somewhat ill-defined fossil, occurs both in the Knoxville and in the 

 Horsetown beds. The A^xa, according to Gabb, occurs in the Horsetown, 

 and he also describes the Pecten from the same horizon.-^ Evidently, then, 

 the beds at Riddles contain a mixture of forms, and the most characteristic 

 fossil of the Knoxville beds is associated with Ammonites of Horsetown age 



*Gabb also mentions the Area and the Pecien as collected from Chico or uppermost Cretaceous 

 beds, and Cardium translucidum is reported in Pal. Cal. only from the Chico be>is. There is some 

 doubt as to the specific ideality of specimens collected in the Chico and Shasta groups (see Pal. 

 (^al., vol. II, 1869, p. xiv). That fossils from these two groups are in a few cases very closely allied 

 is unquestionable. 



