458 MESOZOIC TIME. 



nites have been reported to occur in the overlying rock. But the larger part of the Coal 

 series may be Eocene Tertiary, as held by Hayden and Lesquereux ; and it is described 

 beyond under that head. Still it may turn out that all will have to go together — either 

 all Cretaceous, or all Eocene. 



It is also probable that the Tejon group, the coal-bearing group of California, is an 

 equivalent of the Wyoming coal series, and that this also is Eocene, if true of the other. 

 Gabb states that a species of Ammonites extends through the group to the very top, and 

 affords strong evidence of its Cretaceous age; and this is made stronger by the occur- 

 rence also of three or four species of the Chico group in the Tejon group, e. g., Mactra 

 {Cymbophora) Ashburnerii Gabb., Nucula truncata Gabb., Avicula pellucida Gabb. 

 To show the Tertiary aspect of the shells, the genera are enumerated on page 508. 

 Conrad referred the California beds to the Eocene. 



The Vancouver Island Cretaceous has afforded Inocerami, Trigonia (T. Evansana, 

 M. ) and other Cretaceous fossils. 



Economical Products. 



Mines of Cinnabar, the chief ore of quicksilver, occur at various 

 points in the metamorphic Cretaceous rocks of the Coast ranges of 

 California. The usual associated rocks are serpentine and argillaceous 

 and siliceous slates. The most productive region is that of New 

 Almaden, fifty miles south-southwest of San Francisco. It is worked 

 also at New Idria, in Fresno County, at the Reddington mine in Lake 

 County, and at some other points. 



The Coal-beds, whether Cretaceous or Tertiary, are of great value 

 to the country. They are described under the Tertiary. 



Gold is found sparingly in the metamorphic Cretaceous of California, 

 but has not repaid working. Copper also occurs in many localities, 

 but not in workable veins. Chromic iron is found in the serpentine 

 of California, but not in a condition to repay mining. 



The Green Sand has already been mentioned as a valuable fertilizer. The green 

 grains (called also Glauconite) consist of about 50 per cent, of silica, 20 to 25 protoxyd 

 of iron, 8 to 12 potash and soda (mostly potash), and 7 to 10 water, with also a trace of 

 phosphate of lime. For analyses, see author's "Treatise on Mineralogy." 



II. Life. 



1. Plants. 



With the opening of the Cretaceous period, we find indicated in the 

 rocks a great change in the vegetation of the continent. The Cycads 

 of the Triassic and Jurassic still existed, but they were accompanied 

 by the first yet known of the great modern group of Angiosperms, — 

 the class which includes the Oak, Maple, Willow, and the ordinary 

 fruit trees of temperate regions, — in fact, all plants that have a bark, 

 excepting the Conifers and Cycads. More than one hundred species 

 have been collected ; and half of them were allied to trees of our own 

 forests — the Sassafras (Fig. 825), Tidip Tree (Fig. 826), Plane (or 



