GEOLOGICAL SURVEY OF THE TEERITORIES. 461 



er^d, by tbe higliest autliorities on that department of paleontology, 

 unquestionably Tertiary. 



From tbe foregoing remarks it will be seen tbat our present informa- 

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

 stated as follows : 



1. Tbat it is conformable to an extensive fresb-water Tertiary forma- 

 tion above, from which it does not differ 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 cliaracters from 

 tbe Cretaceous coal-bearing rocks at Bear Biver 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.! 



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 perhaps 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 fresb- 

 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 j) resent epochs, with possibly the exception of 

 Go7iiobasis, (whicb is not yet certainly known from the Cretaceous.) 



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

 tions or subgenera {Leptesthes 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 conspecific with, and two congeneric with, (and 

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

 tbe U])per 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 

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

 with the V. trochiformis of the fresb-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 Viviparus 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 contlicting 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. Banuisters section, fartber on. 



t This fossil, however, I am informed by Professor Losqnoreux, likewise occurs at 

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

 tiary. 



