222 REPORT UNITED STATES GEOLOGICAL SURVEY. 



general sliape from C. vetula, tliey may perliaps be only a variety of tliat 

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

 are often obsolete on C. multistriata, as well as other striated si3ecies. 



31. Odontohasis huccinoides White. 



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

 TJinta MoimtainSj 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 Eocks, where its associates are Ostrea, 

 Anomia, Gorhicula, Corhida, 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 l3een found at various localities as- 

 sociated with brackish-water forms. 



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

 for the study of the Laramie Grrouj) ; and on account of the large number 

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

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

 as they api)ear about a mile south of the station, the point where the 

 greater part of the fossils were obtained: 



Section of Laramie Strata at Black Buttes Station. 



Feet. 



1. TMn bedded sandstones and sandy, ferruginons shales to the top of the Lara- 



mie Group 500? 



2. Sandstone, containing Unio couesi, Campeloma vetula, and Anomia gryi)liorliyn- 



chus 3 



3. Sandy shales, somewhat carhonaceous 4 



4. Shales, containing Cassiopella turrieula, Viviparus plicapressus, Goniohasis grad- 



lienta, Campeloma vetula, Unio dancef , Cortula suhirigonalis, &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 Unio of the foregoing list, Corhicula (Leptesthes) fracta, Melania, 



tvyomingensis, Neritina volvilineata, N. (Velatella) laptista, &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 potats not more than a quarter of a mile distant from 

 each other woidd 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- 

 goiug one was measured, comj)risLQg the exact equivalents of those beds, 



