WHITB.] LARA^IIE FOSSILS OF BITTER CEEEK VALLEY. 217 



23. Tulotoma tliompsoni White. 



2-4. Cam^eloma vctala Meek & Hayden. 



25. Camjjeloma multiliiicata Meek & naj'denl 



NOTES ON THE LARAMIE FOSSILS OF BITTEE CREEK VALLEY. 



As tlie fossils of tlie different localities in Bitter Creek Valley are so 

 closely related they v.ill all be discussed in zoological order iii the follow- 

 iug notes instead of treating those of each locality separately. 



1. Mcmhranipora? 



Upon many of the shells of Ostrea glabra IMeek & Hayden f=0. icyo- 

 minf/ensis IMeek), which were obtained at Point of Rocks, there are small 

 patches of an incrnsting Polyzoan. None of them are quite perfectly 

 preserved, but they are evidently the calcareous cell-bases of a species 

 of Memhranipora or of a closely allied genus. I have detected similar 

 objects at no other locality of Laramie fossils except in the valley of 

 Bear Eiver, but there seems to be no good reason why they may not 

 have existed with any of the many brackish-water siiecies of that period. 

 The}' are iutcrestuig as iudieatiug the continuance of a considerable 

 degi'ce of saltness of the waters untd near or quite the close of the Lara- 

 mie period. 



2. Anomia micronema Meek. 



This species has abeady been discussed upon previous pages as to its 

 geographical distribution and vertical range in the Laramie Groui). A 

 tiew^ small examples of it were found at the Black Buttes locality, and 

 it was also foimd quite abundantly at the Eock Springs locality, but 

 nowhere else iii Bitter Creek Valley. At both those localities it w^as 

 foiuid in a separate layer associsited only "with Ostrea glabra. At the 

 Eock Sprmg's locaUty the examples are of good size, and many of them 

 have a greater than the average convexity of form. 



At none of the numerous localities where this species has been found, 

 from the one reported by Dr. Hayden, two huncbed miles east of Denver, 

 to those of Bitter Creek Valley, none but upper valves have been discov- 

 ered. It is vevj difficult to even suggest an exiDlanation of this remarka- 

 ble fact, which has before been referred to. 



3. Anomia grypliorhynchus Meek. 



The locality two miles below Point of Eocks is the only one that has 

 furnished many examples of this species, although it has been clearly 

 recognized at the Crow Creek locality east of the Eocky Mountains, and 

 also at the Black Buttes and Yaiiipa Valley localities. This shows a 

 wide geographical distribution and a considerable vertical range of the 

 species. As in the case of A. micronema^ none but upi)er valves of this 

 species have been found. 



4. Ostrea glabra Meek & Hayden. 



This species has already been discussed at length on former pages, and 

 reasons given for referring these western forms to 0. glabra j\Icek & Hay- 

 den rather than to regard them as a separate species mider the name of 

 O. wgomingcnsis Meek, the types of which were foimd at Point of Eocks. 

 If it were not for the lately obtained proof that the Judith Eiver, Fort 

 Union, Colorado Lignite and Bitter Creek series all belong to one and 

 the same period, and the discovery of iutermediate forms connecting 

 these two Ibrmerly recognized species of Ostrea, it is not probable that I 

 should have ever susi)cctcd them to be distinct. The lack of intermediate 



