GEOLOGICAL SURVEY OF THE TERRITORIES. 461 



ered, by the liigiiest authorities on that deppirtment of paleontology, 

 unquestionably Tertiary. 



From the foregoing remarks it will be seen that our present informa- 

 tion in regard to the age of the Bitter Creek series may be summarily 

 stated as follows : 



1. That it is conformable to an estensive fresh-water Tertiary forma- 

 tion above, from which it does not diifer materially in lithological 

 characters, excepting in containing numerous beds and seams of coal.* 



2. That it seems also to be conformable to a somewhat differently 

 composed group of strata (1,000 feet, or possibly much more in thick- 

 ness) below, apparently containing little if any coal, and believed to be 

 of Cretaceous age. 



3. That it shows no essential difference of lithological characters from 

 the Cretaceous coal-bearing rocks at Bear Eiver and Coalville. 



4. That its entire group of vegetable remains (as determined by Pro- 

 fessor Lesquereux) presents exclusively and decidedly Tertiary affinities, 

 excepting one peculiar marine plant, {Halymenites,) which also occurs 

 thousands of feet beneath undoubted Cretaceous fossils, at Coalville, in 

 Utah.T 



5. That all of its animal remains yet known are specifically different 

 from any of those hitherto found in any of the other formations of this 

 region, or, with perhaiDS two, or possibly three exceptions, elsewhere. 



6. That all of its known invertebrate remains are mollusks, consisting 

 of about thirteen species and varieties of marine, brackish, and fresh- 

 water types, none of which belong to genera peculiar to the Cretaceous 

 or any older rocks, but all to such as are alike common to the Creta- 

 ceous, Tertiary, and present epochs, with possibly the exception of 

 Goniohasis, (which is not yet certainly known from the Cretaceous.) 



7. That, on the one hand, two or three of its species belong to sec- 

 tioDS or subgenera {Leptestlies and Veloritina) apparently characteristic 

 of the Eocene Tertiary of Europe, and are even very closely allied to 

 species of that age found in the Paris Basin ; while, on the other hand, 

 one species seems to be conspecitic with, and two congeneric with, (and 

 closely related specifically to,) forms found in brackish- water beds on 

 the Upper Missouri, containing vertebrate remains most nearly allied to 

 types hitherto deemed characteristic of the Cretaceous. 



8. That one species of Anomia found in it is very similar to a Texas 

 Cretaceous shell, and perhaps specifically identical with it; while a 

 Viviparus, found in one of the upper beds, is almost certainly identical 

 with the Y. trocMformis of the fresh-water Lignite formation of the 

 Upper Missouri; a formation that has always, and by all authorities, 

 been considered Tertiary. 



9. That the only vertebrate remains yet found in it are those of a large 

 reptilian, (occurring in direct association with the Vivi/parus mentioned 

 above,) which, according to Professor Cope, is a decidedly Cretaceous 

 type, being, as he states, a huge Dinosaurian. 



It thus becomes manifest that the paleontological evidence bearing 

 on the question of the age of this formation, so far as yet known, is of a 

 very conflicting nature ; though aside from the Dinosaurian, the organic 

 remains favor the conclusion that it is Tertiary. The testimony of the 

 plants, however, on this point, although they doubtless represent what 

 would be in Europe considered clearly a Tertiary flora, is weakened by 



* See Mr. Banuister's section, farther on. 



+ This fossil, however, I am informed hy Professor Lesquereux, likewise occurs at 

 numerous localities iu Colorado and elsewhere, in beds he regards as decidedly Ter- 

 tiary. 



