64 CALIFORNIA ACADEMY OF SCIE.VCES. [Proc. 3D Ser. 



and there can be no doubt that many of the species do favor 

 that determination. At the same time, however, it must be 

 admitted that many of them are also more closely allied to 

 forms of the Gault. 



It has been stated by R. T. Hill (1893), that in the Cre- 

 taceous deposits on the eastern border of the Cordilleras 

 a distinct unconformity exists between the strata of the 

 Comanche series and those of the Upper Cretaceous. 

 Rocks of the Dakota epoch are absent from large areas, 

 indeed, from the whole region extending from eastern 

 Texas to Wyoming and westward; while, at the same time, 

 there is evidence of a land-mass covering this belt from 

 which have been derived the littoral conglomerates of the 

 Dakota lying to the eastward. Furthermore, there is a 

 marked difference, both lithological and faunal, between 

 the deposits of the Comanche and those of the Colorado 

 and later groups, which extend far beyond the boundaries 

 of the Lower Cretaceous, reaching northward beyond the 

 region of the Upper Missouri. The rocks of the Comanche 

 series, consisting largely of marls and limestones, indicating 

 deep water conditions, are followed by clays and shales 

 and coarser detrital material, such as could only have been 

 deposited in shallow water. 



The faunal differences are very great, although they 

 cannot be more than referred to here; yet it is worth while 

 recalling the comparisons that have been made between 

 these faunas and their contemporaries upon the Pacific 

 border. Stanton has especially emphasized the contrast 

 which is apparent betw^een the faunas of the Comanche 

 and the Shasta groups. It is not certain to what extent his 

 epitomized diagnosis is applicable for this purpose, since 

 he has included in the Shasta formation the whole of the 

 Horsetown, which evidently has, in large part, no marine 

 representatives upon the eastern border of the Cordilleran 

 continent. The Dakota group, which is the equivalent to 

 at least a portion of the Horsetown, is either absent or is a 

 non-marine, plant-bearing series, but which, moreover, in 

 any case is omitted from any part of the comparison. 



