460 GEOLOGY. 



the bryozoans and most of the minor types. Fishes were also wanting, 

 though the reason is not evident. In a word, the Oriskany fauna was 

 essentially an assemblage of well-fed mollusks and molluscoids with 

 a scant sprinkling of other forms. 



There was a fauna in South America that contained Oriskany-like 

 forms. The Helderberg type is not known to have preceded it there. 

 The wide-ranging habitat along the coast of the Atlantic, which this 

 seems to imply, was probably the main home of the fauna, and its 

 incursion into the interior was probably but an episode in its history 

 which happens to have been better recorded than the main chapter. 



The Onondaga Fauna. 



The presence of true marine fish. — The Onondaga fauna is most 

 strikingly distinguished from the preceding ones by the appearance 

 of a host of fishes of highly developed and divergent types. There is 

 no reasonable ground to doubt that these were true marine fishes, 

 whatever may have been true of the fishes of the late Silurian and 

 of the transition beds discussed in the last chapter, and of the Old 

 Red Sandstone fishes to be discussed later in this chapter under the 

 head of fresh-water life. The Onondaga fishes were intimately asso- 

 ciated with marine invertebrates of the most typical kind, and in the 

 most typical way, and there were none of those peculiar associations 

 with gigantic crustaceans, land plants, and a strange pauperitic group 

 of invertebrates, which seemed to place the previous fish faunas in a 

 special category. Confirmatory of the true marine character of these 

 fishes is the fact that they had successors in the succeeding marine 

 deposits, and left a consistent record from that time to the present. 

 Instead of occasional and sporadic appearances in special localities, 

 such as characterize the record from the Ordovician period up to this 

 time (and which perhaps merely imply occasional incursions or inwashes 

 from land-waters), there was now a continuous occupancy of the seas, 

 for from this time on fishes ranged widely through the epicontinental 

 waters of America and of Europe, and doubtless of the seas generally. 

 Their numbers in the Onondaga waters were very great, though the 

 list of known genera and species is small. A notable feature of the 

 record consists of " bone beds," thin layers made up almost exclu- 

 sively of the plates, teeth, spines, and dermal ossicles of fishes whose 

 numbers must have mounted into the millions. One of these occurs 

 near Columbus. Ohio, and another near North Vernon, Indiana. New- 



