1914] Kew: Tertiary Echinoids of the Carrizo Creek Region 



45 



flows is a stratum' of tuffaeeous material and a thin layer of fine- 

 grained, non-fossiliferous sandstone. The andesite shows a great 

 variety of colors, ranging through red, green, and blue. 



YuJia Buttes Locality. — At Yuha Buttes a series of beds is found 

 which belongs to the Upper Division of the Carrizo formation, being 

 a direct continuation of this division from the foot of Coyote Moun- 

 tain. The beds are well exposed here, as the Buttes form a dome or 

 bowed anticline which is traversed through the middle by a deep 

 gully. The strata are almost entirely sandstone with varying texture, 

 and probably were deposited in shallower water than the beds of the 

 Upper Division in Carrizo Valley. They contain, as common fossils, 

 Pecten circularis, n. var., Ostrea vespertina, and Ostrea heermani, the 

 latter being very abundant in one stratum. 



Faunal Relations 



The region of the Gulf of California has evidently been a distinct 

 faunal province since middle Tertiary time. The fauna is quite 

 different from that of the outer coastal province and is of a more 

 distinctly tropical type. In a comparison of the Recent fauna oc- 

 curring along the coast of Southern California and the west coast of 

 Lower California, with that of the Gulf of California, it is found that 

 only 8.5 per cent of the species are common to the two regions. This 

 dissimilarity also appears in a comparison of the Carrizo fauna with 

 that of the Coast Range formations of approximately the same period. 



The Carrizo fauna has a close resemblance to that found in the 

 Gulf of California at the present time. Like the latter, it is of a 

 distinctly warm-water type and is characterized by the large size of 

 the individuals. It is represented by such genera as Conns, Cassis, and 

 Dolium. This close relation is further strengthened by the presence of 

 several echinoclerms, Encope tenuis, n. sp., Clypeaster deserti, n. sp., 

 Clypeaster bowcrsi Weaver, and Hippo noe calif ornica, n. sp., which 

 have their nearest relatives in the living species Encope calif ornica 

 Verrill, Clypeaster rotundus A. Agassiz, Echinanthus testudinarius 

 Gray, and Hipponoe depressa A. Agassiz, of the Gulf of California. 

 These Recent forms are evidently descended from the Carrizo forms. 

 Each of these four echinoderms of the Tertiary beds shows only slight 

 differences from the Recent species. 



The Gulf of California in Tertiary times extended northward, 

 occupying the Imperial Valley, and was evidently separated from the 

 faunal province of the Pacific Coast of California by a continuous 



