740 



GEOLOGY 



means so ample as would be expected if the deposits were made 

 mainly in lakes and river channels. This is an additional reason 

 for the growing opinion that the terrestrial deposits were in con- 

 siderable part the products of land-wash of the more transient type, 

 due to overflows, storm-wash, sheet-wash, and other forms of more 

 strictly subaerial aggradation. 



Fig. 502. THE COMANCHEAN FAUNA OF THE TEXAN PROVINCE, a-c, Echi- 

 noidx; a, Holaster simplex Shum.; b, Diplopodia texanum Roemer; r, 

 Hemmster dalli Clark, d-h, Peleajpods: d, Anatlna austinensis Vaughan; 

 e, Homomya auxtlnensis Vaughah; /, Trtgonta emori/i Conrad; y, Lima 

 OBBGtttlfa Roemer; h t Peeten tetanus Roemer. i-l, (/v/N/ro/w/x: /, /''M.S//X 

 tetanus. Vatlghan; j, Turritella buflaensts Vatighan; A;, Cerithium (?) t>:r- 

 anum Vaughan; I, Ttochus sp. ffi, a coral, Parasmilia texana Vaughan. 



The marine faunas. Two very distinct marine faunas are found 

 in North America, implying two distinct maritime provinces that 

 of the Mexican Gulf and that of the Pacific. The former had its 

 connections eastward with Portugal and the Mediterranean region, 

 the latter, northward and westward with Asia and Russia, though 

 the boreal element is less conspicuous in the upper part (Horsetown). 

 No species common to the two provinces is known. The decline 

 of the boreal aspect of the western fauna may have been due to the 

 closing of Bering Strait, thus shutting off cold currents from the 

 Arctic. 1 



^tanton, Jour. Geol., Vol. XVII. 



