2l8 NEW YORK STATE MUSEUM 



The convergence of these shells is a consequence of uniform physical 

 conditions, and it has as its result the obliteration of original differences 

 and ancestral generic characters. Hence the determination of phylogeny 

 herein is rendered extremely difficult. Some are doubtless Dimyarians 

 with cardioid affinities (Ontaria, Buchiola, Praecardium), others appear to 

 be allied to the aviculoids and Monomyarians (Posidonia, Kochia, Loxop- 

 teria and probably Lunulicardium, Honeoyea, Pterochaenia). The tenuity 

 of the shell rarely permits any indication of muscular scars. In Lunuli- 

 cardium, Honeoyea and Pterochaenia ontogeny shows that the primitive 

 shell is simple and veneriform in outline, the great hiatus a wholly second- 

 ary development. 



OTHER COMPONENTS OF THE FAUNA 



The Ptcropods are represented by myriads of individuals but only a 

 few species. The Gastropods are more abundant in species, the predomi- 

 nant genera being Loxonema, Phragmostoma, Bellerophon, Tropidocyclus, 

 Palaeotrochus and Pleurotomaria, all of thin shelled forms. Of the 

 BracJiiopods there are few, and these are seldom to be found in association 

 with the characteristic members of the fauna. The only forms known are 

 a Chonetes, a Crania, a small Productella, and three species of Lingula; all 

 are rare and quite certainly survivors of the replaced Hamilton or inter- 

 lopers from the adjoining Ithaca fauna. Of the Corals none are known 

 save species of Aulopora found incrusting the dead shells fallen to the bot- 

 tom, and a small cyathophylloid in the Wiscoy shales. 



The deep littoral habit of this fauna is again indicated by its wide dis- 

 semination. We have observed that no life zone in history maintains its 

 individuality with more persistence and integrity over the earth than this, a 

 fact evinced by the frequency of determinations of identity between the 

 New York and transatlantic species and expressions of close specific rela- 

 tionship in a still greater number of instances, and again by community in 

 strange and peculiar genera at remote manifestations of the fauna, specially 



both are of the same nature [see Simroth. Die Acephalen der Plankton-Expedition. 

 1896. v. 2, F. e, pi. 1, fig. ic]. Planktomya is a shell composed wholly of conchiolin and 

 has been caught at the surface in the waters of the tropical Atlantic. 



