222 KEPOET UNITED STATES GEOLOGICAL SURVEY. 



general shape from C. vetula, they may perhaps be only a variety of that 

 species. This is rendered probable by the fact that the revolving lines 

 are often obsolete on G. multistriata, as well as other striated species. 



31. Odontobasis buccinoides White. 



This species is described in Powell's Report on the Geology of the 

 Uinta Mountains, p. 124. With the exception of a single species found 

 in the Danforth Hills, and doubtfully referred to this genus, only two 

 other species of the genus are known. These are both of Cretaceous 

 age, and are associated only with marine forms. The living affinities of 

 the genus are also with those only of marine habitat, and it is probable 

 that this species actually lived only with those that could endure a con- 

 siderable degree of saltness of the water. It has been found only at the 

 locality two miles west of Point of Bocks, where its associates are Ostrea, 

 Anomia, Corbicula, Corbula, and Melania (insculpta). The specimens of 

 the last-named species may have been drifted to their present association 

 from a more natural habitat, but it is possible they all lived together, espe- 

 cially so since M. wyomingensis has been found at various localities as- 

 sociated with brackish- water forms. 



Bitter Creek Valley is one of the most important districts yet known 

 for the study of the Laramie Group; and on account of the large number 

 of species of its fossils found there the Black Buttes locality is one of 

 especial importance and interest. The following is a section of the strata 

 as they appear about a mile south of the station, the point where the 

 greater part of the fossils were obtained: 



Section of Laramie Strata at BlacTc Buttes Station. 



Feet 



1. Thin bedded sandstones and sandy, ferruginous shales to the top of the Lara- 



mie Group 500? 



2. Sandstone, containing TJnio couesi, Campeloma vetula, and Anomia grypliorliyn- 



chus 3 



3. Sandy shales, somewhat carbonaceous 4 



4. Shales, containing Cassiopella turricula, Viviparity plicapressus, Goniobasis graci- 



lienta, Campeloma vetula, TJnio dance?, Corbula subtrigonalis, &c 1 



5. Bluish, clayey shale, containing fragments of Ostrea and Anomia 5 



6. Calcareous fragmentary layer, containing an abundance of Tutoloma thomp- 



soni, mostly decomposed 1 



7. Calcareous and sandy fragmentary material, very fossiliferous, containing all 



the species of TJnio of the foregoing list, Corlicula {Leptesthes) fracta, Melania, 



wyomingensis, Neritima volvilineata, 2f. ( Velatella) baptista, &c 4 



8. Sandy shales, with alternating calcareous fragmentary layers 30 



9. Dark carbonaceous shales, with Ostrea and Anomia 6 



10. Common sandstones 100 



11. Sandy, grayish shales and soft sandstones 300 



In the neighborhood of Black Buttes Station there are, within the 

 limits of this section, three or four coal or carbonaceous horizons, two of 

 which have been worked for coal. One of these appears to be repre- 

 sented by No. 3, and another by No. 9 of the section ; but all the beds 

 of the series exposed in this neighborhood are so extremely variable that 

 sections taken at points not more than a quarter of a mile distant from 

 each other would hardly be recognized as intended for the same locality, 

 especially in its thinner members. 



The beds of coal are not continuous here, as they usually are in the 

 Carboniferous Coal-Measures ; but from a good workable thickness at one 

 point a bed will disappear entirely within half a mile. The layers con- 

 taining the fossils are equally inconstant as regards their fossil contents, 

 and a measured section half a mile away from the point where the fore- 

 going one was measured, comprising the exact equivalents of those beds, 



