Mesozoic and Camozoic Geology and Palceontology. 143 



range of mountains, but extending as far to the southwestward as the 

 southwest corner of Utah, and its eastern limit is far out on the great 

 plains, east of the Rocky JMountains, where it is covered from view by 

 later formations and the prevailing debris of the plains. These limits 

 indicate for the ancient Laramie sea, a length of about 1,000 miles 

 north and south, and a maximum width of not less than 500 miles. 

 Its real dimensions were no doubt greater than those here indicated, 

 especially its length; and we may safely assume that this great 

 brackish-water sea had an area of not less than 500,000 square miles. 

 The present range of the Rocky Mountains, which has been entirely 

 raised as a mountain range since the close of the Laramie period, 

 traverses almost the entire length of this great area, and far the 

 greater part of the other extensive and numerous displacements which 

 the strata of the different geological ages have suffered within that 

 great area, have also taken place since all the Laramie strata were 

 deposited, although some of those changes thus especially referred to 

 began before the close of the Laramie period. 



The invertebrate fauna consists almost whollj' of brackish-water, 

 fresh-water and land mollusca. Species belonging to all three of these 

 categories are often found commingled in the same strata, but it is 

 also often the case that certain strata, sometimes only thin layers, 

 which contain the fresh-water and land molluscs alternate with those 

 which contain the brackish-water species. All the species of fresh- 

 water and land mollusca which prevailed during the Laramie period, 

 seem to have ceased with the disappearance of their contemporary 

 brackish -water forms, although they were succeeded b3^ other fresh- 

 water and land species. 



He described from 'Point of Rocks' station, Bitter Creek valley, 

 Wyoming, Axinma holmesana; from the mouth of Sulphur creek, 

 Bear river valley, Wyoimng, Bhytophoms meek/ ; from the Cretaceous 

 of Collin county, Texas,. Ostrm blacki, Exogyra wmchelli, Pteria 

 (?) stahilitatis; from Bexar county, Texas, Exogyra forniculata; 

 from Bell county. Texas, Pachymya compacta, Thracia myoiformis; 

 from the estuarj- strata of the ugQ of the 1^'ox Hills Group at Coalville, 

 Utah, Anemia propatoris; from the Fox Hills Group at Cimarron, 

 New Mexico, Barhatia harhidata; from Dodson's Ranch, near Pueblo, 

 Colorado, Lispodesthes obscurata; from the Dakota Group, Saline 

 county, Kansas, Pteria salinensis, Gervillia mudgeana; from the Fort 

 Pierre Group at Fort Shaw near Muscleshell river, Montana, Tessarolax 

 hitzi; and from the Cretaceous of Yellow Stone river, Montana, Fas- 

 ciolaria alien i. 



