CORRELATION WITH EUROPEAN DEPOSITS. 



255 



Cenomanian. Of the 46 species figured by Sowerby as coming from 

 Blackdown, at least 23, or one-half of the entire number, are represented 

 in the Shasta-Chico fauna by closely related species. These include such 

 well marked forms as — 



From Blackdown- 



Astarte striata. 



Cuculhva costellata, 



Cucullsea fibrosa. 



Exogyra conica, 



Mytilus edentulus. 

 Mytilus lanceolatus 



Thetis major. 

 Thetis minor. 



Trigonia aliformis. 



Trigonia dxdalca. 



Trigonia spectabilis 



Turritella granxdata. 



Represented in California by — 



Eriphyla umbonata. (?) 

 Nemodon vancouverensis. 

 ( 'ucullsea truncata. 



Exogyra, parasitica. 



Mytilus lanceolatus. (?) 



Thetis annulata. 



Trigonia evansana. 



Trigonia leana. 



Turritella seriatim-gra n idata. (?) 



In addition to these the Blackdown beds contain a number of species 

 belonging to the Venerida 1 and Aporrhaidse, both of which groups are 

 well represented in the Shasta-Chico fauna. In fact, so far as can be 

 judged by figures and descriptions, the whole fauna of the Blackdown 

 beds, if it had been found in the western part of the United States, would 

 be referred to the Shasta formation and about to the horizon of the 

 Horsetown beds. 



Whether the Chico beds above the fossil-bearing Horsetown horizon 

 represent all the rest of the upper Cretaceous remains to be determined. 

 The close relationship of their fauna to that of the underlying beds which 

 has been compared with the Gault and Cenomanian, and its distinct- 

 ness from the upper Cretaceous faunas east of the Rocky mountains 

 representing the Turonian and Senonian of Europe seem to favor the 

 view that a large part of the upper Cretaceous series is absent from the 

 Pacific coast. 



Conclusions. 



' In view of all these facts, it seems to me that the exact relationship of 

 the Chico and Tejon formations and the extent to which their faunas are 

 connected must still be regarded as an open question that can be solved 

 only, if at all, after exhaustive collections have been made from both 

 formations and thoroughly studied. 



