PREFACE. Xiil 



the San Juan Archipelago, on the north, through Washing- 

 ton Territory and Oregon to Southern California, as well as 

 isolated patches in Eastern Oregon and in Mexico. Except 

 that in Mexico, which seems to be an extension of one of the 

 best-known members of the Texan Group, it is divided into 

 four groups, as follows : 



1st. The Tejon Group, the most modern member, the Di- 

 vision B. of Palaeontology, Vol. I, is peculiar to California. 

 It is found most extensively developed in the vicinity of Fort 

 Tejon and about Martinez. From the latter locality it forms 

 an almost continuous belt in the Coast Ranges to Marsh's, 

 fifteen miles east of Monte Diablo, where it sinks under the 

 San Joaquin plain. It was also discovered, by the different 

 members of the Survey, at various points on the eastern face 

 of the same range, as far south as New Idria, and, in the 

 summer of 1866, by Mr. Gabb, in Mendocino County, near 

 Round Valley, the latter locality being the most northern 

 point at which it is as yet known. It is the only coal-pro- 

 ducing formation in California. 



This group contains a large and highly characteristic series 

 of fossils, the larger part peculiar to itself, while a considerable 

 percentage is found extending below into the next group, 

 and several species still further down into the Chico Group. 

 Mr. Gabb considers it as the probable equivalent of the 

 Maestricht beds of Europe. 



2d. The Martinez Group is proposed provisionally, to in- 

 clude a series of beds, of small geographical extent, found at 

 Martinez and on the northern flank of Monte Diablo. It 

 may eventually prove to be worthy of ranking only as a sub- 

 division of the Chico Group. 



3d. The Chico Group is one of the most extensive and im- 

 portant members of the Pacific coast Cretaceous. Its exact 



