58 CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



proportion of cephalopods is essentially the same in each. 

 Although in the case of the Phoenix beds it seems somewhat 

 large, this is due rather to the neglect of the lower orders 

 than to their absence. It is not far from the truth to say 

 that the ratio of the cephalopods to the others is, in general, 

 one to five. The genera most commonly present in this 

 class are Pachydisciis, JBaculites, Hamites, and others of the 

 aberrant types. A few species of Desmoccras, Lytoceras^ 

 and at least one species of Phylloccras are known to occur. 

 Phylloceras ramosum (Meek) is common to the three basins, 

 occurring at Mount Diablo, the " Forty-nine Mine," and in 

 the Nanaimo beds. Baciilites chicoensis is reported from the 

 Chico and Nanaimo groups along with Pachydiscus nciv- 

 berryaiius, and possibly P. sucta'ensis ; while the Nanaimo 

 and the Phoenix beds are further connected by Lytoceras 

 jukesi, and by representative species of Hamites and Bacu- 

 lites. Similarly the connection between the Chico and the 

 Phoenix beds is reinforced by the occurrence in each of 

 Schlanhachia chico'ensis{^x'A.^\C), and an Acanthoceras related 

 to A. rotomagense. Undoubtedly, however, the strongest 

 connections between the three basins are shown by the 

 large proportions of gasteropods and bivalves, very many of 

 which are specifically common to all of them. In addition 

 to Inoceramtis lahiatus, which is common to all the basins, 

 there is also /. crippsi, which is probably identical with 

 /. whitneyi. Two species of Trigonia, — T. tryoniana and 

 T. evansana, — are found alike in each of the three basins. 

 But the true relations can only be fully presented by com- 

 parative lists of species, such as the one published by Whit- 

 eaves, which cannot here be reproduced. Of the thirty or 

 more species there listed as common to the Nanaimo and 

 the Chico beds, more than half are found in the Phoenix 

 (and later) beds of the Oregon Basin. Others, common 

 only to the Phoenix and Nanaimo beds, and others, occur- 

 ring only in the Phoenix and Chico beds, still further 

 augment this number; and this is exactly what would be 

 expected in beds synchronously deposited in different 

 basins. 



