242 GEOLOGY OF THE DENVEK BASIN. 



fossils were found. The species are Ostrea glabra M. >S: II., Corbula subtrigonalis 

 M. <£ II., Modiola regularis White, and a few other indeterminate forms. Specimens 

 of Ostrea were obtained to within 100 feet of the coal. 



Above the Castle Gate coal mine there are about 300 feet of alternating brownish 

 sandstones and shales, with several seams of coal and some thin, calcareous bands, in 

 one of which, about L50 feet above the main coal bed, a few species of fresh-water 

 mollusca were found. These include Viviparus panguitchensis White, Viviparus 

 trochiformis M. & 11.. Goniobasis tenuicarinata M. & 11., and indeterminate species 

 of Bulinus, Physa, Limncea, Planorbis, Unio, and Sphwrium. They show rather close 

 relationship with the fauna that occurs at a much higher horizon. 



Next in ascending order is a series of heavy-bedded, brownish-gray sandstones 

 usually forming vertical cliffs and having an estimated thickness of 800 or 1,000 



feet. At I he loot of one of these cliffs, just north of Castle Gate, s e bones of 



a large reptile were found in a mass of sandstone that had evidently fallen from 

 the cliff. These were submitted to Prof. O. C. Marsh, who reports that "they agree in 

 essential particulars with the type specimens of Claosaurus annectens, which occurs 

 in the Ceratops beds of the upper Laramie of Wyoming."' 



Overlying this massive sandstone is a series of similar sandstones in beds I'd 

 or 30 feet thick, alternating with shales, and having a total thickness of about 300 

 feet, and these merge into a series containing a greater proportion of shale and 

 some bands of fresh-water limestone in which invertebrate fossils are very abundant, 

 including the following: 



Unio meiidax White. Goniobasis filifera White. 



Physa pleromatis White. Liminea tenuicostata M. & H. 



Viviparus trochiformis M. & II. Hydrobia ntahensis White. 



Viviparus leidyi M. & H. Cypris saupetensis White. 



Goniobasis tenuicarinata M. >\ II. 

 These all occur in the lower portion of the series referred by Dr. <'. A. White 

 to the Wasatch formation (Bull. U. S. G. S. No. 31, p. 10) on the higher hills near 

 Castle Gate and at Pleasant Valley Junction and other localities in that region. 

 Several of the species are identical with forms that occur in the fort Union beds on 

 the Missouri River, and some of them also occur in beds believed to belong to the 

 true Laramie of Colorado and Wyoming. 



The entire series from the marine Cretaceous up into the fresh-water Eocene 

 seems to be conformable, and there are no sudden changes in the character of the 

 sediments. The close relationship, and in some cases specific identity, of the fresh- 

 water mollusca in the coal-bearing series and in the Wasatch also favor Dr. White's 

 view that sedimentation was continuous from the one into the other. 



From Castle (Lite the Laramie coal beds may be traced with practical 

 continuity to Grand River in Colorado, about ISO miles, and at the latter 



