HISTORICAL REVIEW. 437 



coast and to the Gold belt of the Sierra Nevada, the studies of Dr White* 

 and Dr Becker f resulted in changiug the grouping of the Cretaceous 

 sediments. They recognized both the Tejon and the Chico, but they 

 considered them as belonging to the same continuous series of beds, the 

 upper or Tejon portion belonging to the Eocene, the Chico to the Creta- 

 ceous. They gave the joint name Chico-Tejon to this set of beds, as indi- 

 cated in the second column of the table. 



Dr Becker discovered near Wallala, on the coast some miles north of 

 San Francisco, a series of interesting fossils containing forms which had 

 not been previoush^ recognized. The beds in which they were found he 

 called the Wallala l:)eds. Dr White described the fossils, of which the 

 most characteristic is Coralliochama orciUti, and concluded, from paleon- 

 tologic grounds alone, that these beds belong immediately beneath the 

 Chico. According to Dr Becker they rest unconformably upon the 

 metamorphic rocks. 



The beds exposed at Horsetown and elsewhere in Shasta count}^ they 

 called the Horsetown beds, while others, in which the characteristic fossil 

 is of the genus Aucella and well exposed near Knoxville, in Napa county, 

 they called the Knoxville beds. At first, although the Knoxville was 

 recognized by paleontologic evidence as being older than the Horsetown 

 beds, it was supposed that there was a considerable interval of time 

 between their periods of deposition. Owing to the investigations of Dr 

 Becker at Riddles, in Oregon, as well as those of Mr Diller at the same 

 place and in Shasta and Tehama counties, California, it was shown % 

 that these two sets of beds were more closely related than had been pre- 

 viously supposed, so that in his correlation bulletin § of the Cretaceous 

 formations of tlie United States Dr \Miite suggests that their successive 

 deposition took place without a time interval. 



During the last ten years the writers have had an excellent opportunity 

 to study the Cretaceous of the Pacific coast, especially in northern Cali- 

 fornia and Oregon, and also to some extent in the state of Washington. 

 The results are expressed in the fourth column of the accompanying talkie. 



In Oregon the Tejon is entirely distinct from the Chico. It rests with 

 a marked unconformity on the Cretaceous of that region, and is separated 

 from it by a time interval during which there was considerable erosion. 

 In northern California the Tejon is absent, but in middle and southern 

 California it is well represented, and, according to many observers, is 

 conformable with the Chico. 



It has recently been shown by Mr Gilbert D. Harris || that the Tejon 



* U. S. Geol. Survey, Bulletins nos. 15, 22 and 82. 

 tibid., Monograph XIII and Bulletin no. 19. 

 X Bull. Geol. Soc. Am., vol. 2, pp. 201-208. 

 gU. S. Geological Survey, Bulletin no. 82, p. 1S4. 

 II Science, vol. 22, p. 97, August 18, 1893. 



