530 



THE COMANCHEAN PERIOD 



448. It probably had at- 

 tained considerable impor- 

 tance through the extension 

 of the fresh waters, but the 

 record is by no means so 

 ample as would be expected 

 if the deposits were made 

 mainly in lakes and river 

 channels. This is an addi- 

 tional reason for the grow- 

 ing opinion that the terres- 

 trial 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. 



d e 



FRESH-WATER FOSSILS OF THE 

 COMANCHEAN (Lower Cretaceous) from 

 Montana, a and b, Pelecypods: a, Unio 

 farri Stanton; b. Unio douglassi Stanton; 

 c-e, Gastropods: c. Viviparus montanensis 

 Stanton; d, Goniobosis (?) ortmanni Stanton; 

 e, Campcloma harlowtonensis Stanton. 



Fig. 449. COMANCHEAN FOSSILS OF THE TEXAN PROVINCE, a-c, Echinoids: 

 fl, Holaster simplex Shum.; b, Diplopodia texanum Roemer; c, Hemiaster dalli Clark. 

 d-h, Pelecypods: d, Anatina austinensis Vaughan; e, Homomya austinensis Vaughan; 

 /, Trigonia emoryi Conrad; g, Lima wacoensis Roemer; h, Pecten texanus Roemer. 

 i-l, Gastropods: i, Fusus texanus Vaughan; j, Turritella budaensis Vaughan; k, 

 Cerithium (?) texanum Vaughan; /, Trochus sp.; m, a coral, Parasmilia texana 

 Vaughan. 



Marine faunas. Two very distinct marine faunas are found in 

 North America, that of the Mexican Gulf and that of the Pacific 



