COMANCHIC PERIOD 585 



enia, Monopleura, Eadiolites, Nerinea, and corals, thus resembling that of 

 the "Schrattenkalk" of the Urgonian. 



The Washita continues the Fredericksburg fauna, but the characteristic 

 species are Pachy discus brazoensis, Hamites fremonti, Schlcenbachia of 

 the type S. inflata, and Turrilites brazoensis. The Upper Washita is con- 

 sidered basal Cretacic, and is so represented on the paleogeographic maps. 



Pacific area. — In California Comanchic, or, rather, Shastan, time began 

 with the Knoxville, a somewhat restricted marginal invasion with boreal 

 or Aucella faunas. It was in the Upper Knoxville that more extensive in- 

 undation took place to the north of the Sierra Nevada uplift — that is, it 

 extended widely across Alaska, connecting the Pacific with the Arctic 

 ocean. At the same time much of British Columbia was marginally in- 

 vaded by the sea with a boreal fauna distinguished by Aucella crassicollis. 

 At the close of the Knoxville, Alaska was again above the sea, thus shut- 

 ting out the boreal waters with their northern faunas. In California the 

 Knoxville has a thickness of from 12,000 to 20,000 feet. On Queen 

 Charlotte islands the depth of divisions C, D, and E, referred to the Shas- 

 tan, seems to be nearly 9,000 feet. 



According to Stanton, 243 the fauna of the Knoxville is especially marked 

 by an abundance of Aucella piochii in the lower beds and A. crassicollis 

 in the upper 2,000 feet. He states that they are "so abundant that they 

 must have actually monopolized the sea bottom." Among Mollusca the 

 Turbinidag are noteworthy. The more characteristic ammonites are: 

 Pliylloceras knoxvillensis, Desmoceras calif 'ornicum, Olcostephanus muta- 

 bilis, Hoplites hyatti, H. storrsi, H. angulatus, H. crassiplicatus, and H. 

 dilleri. These faunas are correlated with the Neocomian. 



The faunas of the higher Shastan series or the Horsetown are at first 

 much like those of the Knoxville, but the great changes in Alaska brought 

 about by shutting out the boreal waters soon allowed the introduction of 

 the Mediterranean faunas. As a whole, the Horsetown fauna is remarkably 

 distinct from that of the Knoxville, and the former can usually be identi- 

 fied by the absence of Aucella. In its typical development this fauna, 

 however, is restricted to northern California and Oregon, but late Horse- 

 town time is represented as far north as Queen Charlotte islands. 



"Toward the close of the Horsetown the fauna was greatly modified by the 

 introduction of many types that show relationship with the Cretaceous faunas 

 of southern India, and also with those of Japan. This relationship was con- 

 tinued in the succeeding Upper Cretaceous faunas to such an extent that it is 

 appropriate to speak of an Indo-Pacific province or region." 244 



243 Ibid., 1897. 



2 « Stanton : Ibid., 1909, p. 415. 



L— Bull. Geol. Soc. Am., Vol. 20, 1908 



