68 
PALAEONTOLOGY OF NEW YORK. 
The specimen originally described as Euomphalus ? rotundus still retains a 
portion of the shell, bearing the same characters as authentic examples of 
Pleurotomaria Lucina —preserving, however, an unusually broad and deep 
umbilical depression. 
The species has had a wide geographical distribution, and its vertical range 
is not less than one thousand feet from the base of the Upper Helderberg lime¬ 
stone to the higher members of the Hamilton group. 
Formations and localities. In the Corniferous limestone; Helderberg moun¬ 
tains, Williamsville, Clarence Hollow, N. Y., and Falls of the Ohio river; in 
the Hamilton group, York, Moscow, Geneseo, Skaneateles lake, etc., N. Y. 
Pleurotomaria Hebe. 
PLATE XIX, FIGS. 2-7. 
Pleurotomaria Hebe, Hall. Fourteenth Rep. N. Y. State Cab. Nat. Hist., p. 105. 1861. 
“ “ “ Fifteenth Rep. N. Y. State Cab. Nat. Hist., pi. 5, figs. 7 and 8. 1862. 
“ “ “ Illustrations of Devonian Fossils: Gasteropoda, pi. 19. 1876. 
Shell subhemispheric, conical above, rounded upon the lower side; the volu¬ 
tions flattened on the upper side, and nearly in the same plane from the 
apex to the outer edge of the last one ; the spire above the aperture 
about equal to the height of the aperture. Volutions four or more, very 
gradually expanding to the last one, which is moderately ventricose and 
subangular at the limit of the periphery with the upper sloping surface. 
Aperture somewhat transverse, broadly subelliptical. 
Surface marked by strong, revolving strife, and finer transverse ones, which 
are strongly bent backwards on the carina of the outer volution; strife 
not so strong below the peripheral band. 
This species is smaller than either of the preceding, but is' larger and more 
rotund than the P. sulcomarginata of the Hamilton group. The specimens 
examined are all imperfect, and the shell, where remaining, is crystalline, 
impairing the surface characters. The rotundity of the lower side and the 
depressed conical form above, are characteristic features of distinction. 
Formation and locality. Upper Helderberg group, Clarence Hollow, N. Y. 
