38 Crandall — Santa Clara Valley Region in California. 



and northwest edge of the Pleasanton Quadrangle. South of 

 Niles canyon the Cretaceous appears where the Tertiary has 

 been eroded from the hill tops, east of JSfiles, and it is also ex- 

 posed on the west side of Sunol canyon, extending southwest- 

 ward to form the underlying part of the hills rising between 

 the Calaveras and Santa Clara valleys. 



Cretaceous shales are exposed in Niles canyon, showing 

 numerous folds. The Cretaceous of this region consists of three 

 series of beds. North of JSTiles canyon and south of Hay wards 

 pass there are large areas that are covered with massive con- 

 glomerates, the main constituents of which are bowlders of 

 quartz porphyry and biotite granite. The conglomerates are 

 probably the same that Mr. Turner described from Mt. Diablo. 



South of these conglomerates is a thick series of hard, thinly 

 bedded black shales with occasional sandy layers. From these 

 shales on the north bank of Stony Brook Creek, about three 

 miles north of Farwell station in Niles canyon, was collected 

 an indeterminable Ammonite. Another Ammonite came from 

 these same black shales on the west bank of Sunol canyon, at 

 the point where the Mission Peak road enters the canyon from 

 the west. 



The third locality where fossils were collected is on the south 

 bank of ISIiles canyon about one and a quarter miles northeast 

 of ISfiles. and about due south of the station of Meriendo. A 

 small fossiliferous concretion of hard flinty limestone was found 

 here, but it' was possible to get only one good specimen. This 

 specimen was identified as Venus varians. Several hundred 

 yards east, up the canyon, Aucella Piochi was found in black 

 shale. 



Aucella crassicollis was found on the north side of Mission 

 Creek, along the Mission Peak road, about three miles slightly 

 northeast of the town of Irvington. With it were fragments 

 of Venus-like shells. At this place the Tertiary rests uncon- 

 formably upon the Cretaceous. 



The beds in Niles canyon, in which Venics varians was found, 

 are several hundred feet higher in the section than those from 

 which Aucella crassicollis were obtained. In the general level- 

 ling of the Cretaceous sediments, before the deposition of 

 Tertiary, uneven erosion must have left caps of Horsetown 

 upon the Knoxville. The beds from which Venus varians 

 was taken are conformable with the Knoxville beds in which 

 Aucella Piochi are found. No specimens of A. crassicollis 

 were found in the Niles canyon section, but there are several 

 hundred feet of sandstone between the two horizons determined 

 by the fossils found. These intervening beds may represent 

 the horizon of Aucella crassicollis. 



Jordan's Panc/i, Arroyo del Voile. — From Jordan's ranch 

 in Arroyo del Valle, eight miles southeast of Livermore, the 



