NAPLES FAUNA IN WESTERN NEW YORK, PART 2 215 



Bionomic character of the fauna 



Throughout the components of this fauna there is a striking homo- 

 geneity of character expressed in the fact that all classes of invertebrate 

 organisms are thin shelled, a condition compromised solely by the presence 

 of a few representatives from the adjoining fauna to the east. We have 

 observed in discussing the cephalopods that beyond question the large 

 representation of the Goniatitinae is an actual constituent of the fauna, 

 not strangers or interlopers from some outside region. The known 

 benthonic characters of Nautilus lead rationally to the predication of 

 similar benthonic habits for all the coiled cephalopods of this congeries. 

 Similarly, in other groups we have distinguishing marks of deep littoral 

 habit, which is of itself indicated by the thinness of the shell in all. 



The prevailing species of the lamellibranchs are the Lunulicardia. 

 Even the largest of these must have been of very tenuous shell, and they 

 were all closely attached and dependent organisms, as shown by the great 

 development of the byssal aperture. All the other lamellibranchs are thin 

 shelled. The gastropods, with the exception of Palaeotrochus, which we 

 know to have existed in earlier rocks and to have continued into a still later 

 stage, were thin shelled. There is no reliable indication throughout the 

 fauna of shallow water habit even in the attached Lunulicardia and but 

 few of true pelagic habit. It is quite likely that the set of the coastal 

 current established by the temporary submergence of the northwest barrier, 

 which allowed this fauna to enter the Appalachian gulf for a while, brought 

 with k masses and tangles of the great algae that are found in these rocks, 

 Dadoxylon and Nematophycus, of which we know portions of the stock 

 having a length of fully 20 feet and a girth equal to that of a man's body ; 

 these doubtless afforded a base of attachment for the numerous thin shelled 

 byssus-bearing lamellibranchs. The deep water conditions are also corrob- 

 orated by the evidence derived from the presence of the bituminous shale 

 beds. If the latter on the whole indicate the depths of the gulf below the 

 line of flourishing life, and their organisms are largely those of the upper 



