14 . PALAEONTOLOGY. 



corresponded in the sequence of geological changes here to that event 

 seems probable. 



In the vicinity of Fort Bridger, Tertiary deposits exist, apparently of 

 later date than the Bear Eiver beds that have furnished the fossils men- 

 tioned above. So far as yet known, these Fort Bridger beds contain only 

 fresh-water and perhaps terrestrial fossils. From this formation, the fol- 

 lowing species, figured on plate 17, were collected, mainly by Colonel Simp- 

 .son's party, viz., Limncea similis, L. vetusta, Goniohasis Simpsoni, Planorhis 

 spectabilis, and P. spectahilis, var. UtaJiensis; also Unio Haydeni, figured on 

 plate 1 6. So far as known, all the species from this formation are distinct 

 from those found in the Bear River deposits; and only one species, Planorhis 

 spectahilis^ is very nearly related to any species found on the upper branches 

 of the Missouri. 



A few fossils in the collection, from the region of Fossil Hill, Kawsoh 

 Mountains, Nevada, show that thei:e is there an exceedingly interesting 

 Tertiary formation. These fossils are in a beautiful state of preservation, 

 and contained in a white, soft limestone, or indurated marl. Not a single 

 one of the species yet known from this formation is identical with any of 

 those hitherto discovered in any of the other Far- Western Tertiary deposits.* 

 They are all fresh-water forms, and consist of the following species, viz., 

 SpJicBrimn IdaJioense and S. rugosum, figured on plate 16, and Carinifex 

 Tryoni, C. JBinneyi, Goniohasis sculpfilis, G. suhsculptilis, and Ancylus undu- 

 latus, figured on plate 17. The species all being new, and the rock not 

 having been seen connected with any of the other Tertiary formations of 

 that region, we have no means of determining its exact position in the 

 Tertiary series ; though it is probably more recent than either of the other 

 formations from which fossils are figured and described in this report. It 

 will probably yield a large number of new and interesting fossils to who- 

 ever may be able to explore it thoroughly. 



As it has been thought desirable to give as full and complete an 



* At the time of writing the above, I had overlooked the possible identity of the 

 species 1 have described under the name Goniohasis sculpUUs with Melania Taylori, 

 Gabb, described in vol. II, p. 13, Palseout. California, from apparently the same forma- 

 tion in Idaho.— F. B. M., Nov., 1874. 



