366 PALAEONTOLOGY OF NEW-YORK. 



Under other conditions, the plications are more numerous and rounded, the 

 squumose imbricating linos loss conspicuous, and the shell takes a more orbicu- 

 lar form, approaching to the L. flabellites ; but the beak is never so strongly 

 incurved as in that species. It may l)e doul)tful whether an examination of a large 

 number of specimens will sustain a separation from L. {A.) flabellites ; but while a 

 considerable number of individuals from two or three localities sustain the charac- 

 ters originally given, I shall retain it under a distinct specific name. 



Geological foi-malion and localities. This, species occurs in the Upper Helder- 

 berg limestone, near Waterville and at Cassville, Oneida county ; at " Dry-lots," 

 Herkimer county ; at Janiesville, Onondaga county, and at East-Victor, Ontario 

 county. Specimens from the same horizon at Waterloo in Seneca county have a 

 more orbicular form, with more numerous and less angular plications. 



With our present knowledge of the characters of the Genus Leitoc(Elia, the 

 L. flabellites, L. fimbriuta and L. aculiplicata will remain as typical forms of the 

 genus, while Leptocoelia concava, and L. dichotoma (Pal. New-York, Vol. iii, pp. 245 

 and 452) must be referred to the Genus Qelospira ; to which may be added the 

 L. {Atrypa) disparilis of the Niagara group. 



The species Leptocoelia {^Atrypa) hemispheinca ( Pal. New- York, Vol. ii, pa. 74, 

 pi. xxiii, f. 10) and L. {A.) planoconvexa (Ibid. pa. 75, pi. xii'm, f. 11 ; and Vol. iii, 

 pi. ciii B, f. 4 and 5) are apparently true Ljbptoccelia, both from external form 

 and from what we know of their- internal structure. I nevertheless regard it as 

 desirable to make critical examinations of the Clinton group species, in the hope 

 of arriving at a more satisfactory knowledge of their internal structure and 

 relations. 



