.218 EEPORT UNITED STATES GEOLOGICAL SUEVEY. 



forms west of tlie moimtains like tliose wliich were foimd in Eastern 

 Colorado is suggestive tliat'there may after all be really two species, 

 especially so since only thin, small examiDles are found at tke locality 

 two miles west of Point of Eocks. In Professor Powell's Eeport on the 

 Geology of the Uinta Mountains I gave the name of 0. insecuris to these 

 last-mentioned examples, but comparison of my types directly with those 

 of 0. glabra shows too little difference to be satisfactorily regarded as 

 specific. Comparison of large collections made at the typical localities, 

 Point of Eocks and Black Buttes Station, with the types themselves, 

 leaves no doubt in my mind that 0. wyomingensis Meek and 0. arcuatilis 

 Meek are specifically identical. It will of course be imderstood that I 

 regard such forms as the types of 0. glabra Meek & Hayden, 0. suhtri- 

 gonalis Evans & Shumard, and 0. insecuris White as young examples of 

 the species, and 0. wyomingensis Meek as adult forms of the same. By 

 these and other remarks on previous pages it will be seen that at present 

 I recognize only one species of Ostrea in aU the Laramie Group, unless 

 the obscure one that is found in Bear Eiver YaUey, yet to be noticed, 

 shall prove to be distinct from 0. glabra. 



5. Volsella (Brachydontes) regularis White. 



A few large but imperfect examples of this species were found just 

 east of Eock Springs, which is the only locality in Bitter Creek Valley, 

 at which it was discovered. See further remarks under the head of notes 

 on the Laramie fossils of Crow Creek YaUey. 



6. Unio eouesi White. 



This is one of nine or ten species of Unio that have been found asso- 

 ciated in one and the same layer at Black Buttes Station, and also asso- 

 ciated with Corbicula {Leptesthes) fracta, Neritina vslvilineata, Neritina 

 ( Yelatella) baptista and Melania wyomingensis. None of these species of 

 Unio have been discovered at any other locality west of the Eocky Mount- 

 ains, but two of them, U. cryptorhynclms White and U. danw Meek & 

 Hayden, have been somewhat satisfactorily identified with the tjTpical 

 forms from the Upper Missouri Eiver region. This is the largest species 

 of the genus that has yet been found fossil in any strata of the West, It 

 was originally described by me under the name of U. petrinus in Powell's 

 Eeport on the Geology of the Uinta Mountains, p. 125, together with 

 Nos. 7 and 8 following. That name being preoccupied, it was changed 

 to U. eouesi^ in BuU U. S. Geol. and Geog. Sur. Terr., vol. iii, p. 605. 



a uZ fS^SlI White. } ^""^ ^^^^^^^ ™^^^ ^«- ^' 



9. Unio proavitus White. 



This species, together with ISTos. 10 and 11 following, are described ia 

 BuU. U. S. Geol. Sur. Terr. vol. iii, pp. 603 and 604. 



10. Unio Jiolmesiamis White. ) C3 i i at /• 



11. Unio endlichi White. J See remarks under No. 6. 



12. Unio aldricM White. 



This species, together with No. 13 following, are described ia Bull. U. 

 S. Geol. Sur. Ter. vol. iv, pp. 709 and 710. 



13. Unio goniambonatus White. 

 See remarks under No. 6. 



14. Unio cryptorJiynclius White. 



Some imperfect examples found associated with the foregoing species 

 appear to be specifically identical with the types of U. cryptorliynchus 



