THE AGE OF TDE LIGNITIC FORMATION BY ITS FAUNA. 27 



conclusive; for it seems that tlic author slioiild rather have admitted Point 

 of liocks, with Ihe two species of Ostrea, as Tertiary, tlian to liave considered 

 Hallvillc as Cretaceous, for the species of Molhisks are not more evidently 

 Cretaceous than are the Oyster shells of Point of Rocks. The Ostrca of Mar- 

 shall and I'ryant's coal mines are not less marine; species than those of 

 Point of Rocks. This seems the more surprising, that, considering further 

 the question of the age of the group, after discovering in the rocks of the 

 Bitter Creek series between three and four times as many species of fo.ssils 

 as had been known from the same, the celebrated prores.sor remarks, with that 

 adminible candor of mind which adorns all his work: — 



"Although partly committed in favor of the opinion that this formation 

 belongs to the Cretaceous, and still provisionally viewing it as most prol)ably 

 such, I do not wish to disguise or conceal the fact that the evidence favoring 

 this conclusion (o be derived from the Molhisks alone, as now known, is by 

 no means strong or convincing. The genera are probaljly ail common both 

 to the Cretaceous and Tertiary as well as to the present epoch, unless Leptes- 

 thcs and Vcloritina, which have been separated subgenerically from Corhkula, 

 may be distinct genera; the European representatives of these being mainly, 

 if not entirely, Tertiary Ibrm.s, while they do not appear to include living species. 

 Cj oniohasis is also not known in cither Cretaceous or Tertiary rocks of the 

 Old World, but then it is an American type, greatly developed among our 

 existing Molhisca, as well as in the far Western Tertiary Rocks, and we can 

 scarcely doubt that it will be found in un<jiiestionable Cretaceous beds there, 

 even if some of the imperfect si)ecimens already known from the same are not 

 sucli. It should be remembered, however, that even the specimens I have 

 referred to this genus from Bitter Creek beds are not in a condition to show 

 the aperture beyond douljt to possess the characters of Ooniohasis. 



''The entire absence among the fossils yet known from this formation of 

 BacuUtis, Scnphitcs, Ancyloceras^ Ptychoceras, Amjnoniles, Gyrodes, Anchurn, 

 Inoccramus, and all the other long list of genera characteristic of the Creta- 

 ceous, or in part also extending into older rocks, certainly leaves its Molluscan 

 fauna with a strong Tertiary facies. Nor can we quite satisfactorily explain 

 this away, on the ground thai the water in which this series of rocks was 

 deposited partook too much of the character of that of an estuary, to have 

 permitted the existence of any of these marine genera, because we do find 

 in it the genera Ostrea, Anomia, and Modiold, which prol)al)ly required water 



