NIAGARA GKOUP. 



REMAINS OF FISHES. 



319 



Thus far all the remains of fishes, the only class of vertebrata existing at this period so far as 

 we have been able to discover, consist of imperfect and obscure fragments of bones. Probably 

 all those in the Clinton group are parts of defensive fin-bones of one or two species, since 

 they present no marks by which we are able to recognize distinctions between them. 



Many years since, I discovered in the Niagara shale at Rochester the impression of a part of 

 an ichthyodorulite several inches in length, but it was too imperfect to give any satisfactory 

 description. The second discovery of any thing of this kind in the Niagara shale, consisted of 

 the base of one of these spines or defensive fin-bones, found by Col. Jewett at Lockport in 

 1847. Tlie first specimen found exhibited only that portion originally imbedded in the flesh, 

 presenting beautiful and almost symmetrical markings upon its surface, which were probably 

 for muscular attachments. So unlike the markings of any fish remains was this specimen, that 

 it was regarded as belonging to the Crustaceans rather than the Fishes. Some time afterwards^ 

 however, a very fortunate discovery by the same gentleman enabled us to determine the nature 

 of the specimen previously found ; for in the second instance, a beautiful spine of six inches 

 in length was terminated at its base by an enlargement for the muscular attachment, having 

 the same form and markings of the surface as the previous one, leaving no longer any doubt 

 as to the identity of the two. 



No other specimens have since rewarded the labors of collectors, and we may conclude that 

 they are exceedingly rare. 



It is extremely interesting to be able to present, from this geological period, a well marked 

 specimen of this kind, which exhibits not only the characters of the genus, but also shows 

 from the size that it belonged to a large fish. The base of the larger specimen proves more 

 conclusively that the species must have attained a very large size and great weight ; for the 

 portion of the spine still remaining, and which was originally imbedded in the flesh, is more 

 than two inches in length, and one inch and a quarter in diameter just above the base. 

 This is, perhaps, the largest specimen of this kind known ; and we have not yet discovered, in 

 our Onondaga and Corniferous limestones, any thing equalling it in size. A single specimen of 

 another species in the Delthyris shaly limestone (silurian) is nearly as large as this one ; while 

 of a considerable number known in our higher strata, not one equals this in its dimensions. 



The occurrence of fishes even so low down in our series as this, has been for a long time 

 doubted, and we have yet no evidence of the existence of this class of animals in our lower 

 silurian strata. Notwithstanding the immense number of specimens of other organisms (and 

 of species to the number of more than 400) which have been collected from the lower silurian 

 rocks of the United States, not a single fragment of an ichthyic character has fallen under 

 my observation, though I have examined numerous localities extending over a large area 

 between the Hudson and the Mississippi rivers ; and when we reflect that there are, scattered 



[PAL^EONTOLOGy — Vol. ii.] 40* 



