GASTEROPODA. 
27 
“ Locality . Near Schoharie, in Onondaga limestone.” 
A specimen, which has been supposed to represent the original of Mr. Con¬ 
rad, is illustrated in figs. 25 and 26, plate 9. The apparent band bordering 
the suture is caused by a narrow depression of the surface, parallel with 
the suture, from which the striae rise abruptly and bend forward, leaving a 
narrow depressed line or canaliculation along the suture. It has not the 
defined band of Pleurotomaria, and the recurving of the striae is less distinct 
and abrupt than in some other specimens of Platyostoma. 
Formation and locality. In limestone of the Upper Ilelderberg group, Scho¬ 
harie, N. Y. 
Platyostoma unisulcata var. 
PLATE XI, FIGS. 1-3. 
Platyostoma unisulcata var., Hall. Illustrations of Devonian Fossils: Gasteropoda, pi. 11. 1876. 
This form, from the Hamilton group at West Bloomfield, N. Y., has so much 
the form and aspect of Mr. Conrad’s original figure ut cit., except in the lesser 
elevation of the spire above the last volution, and the absence of a sutural 
band, that I have placed it under the above designation. 
Platyostoma turbinata. 
PLATE IX, FIGS. 12-24. 
Platyostoma turbinata, Hall. Fourteenth Rep. N. Y. State Cab. Nat. Hist., p. 106. 1861. 
“ “ “ Illustrations of Devonian Fossils: Gasteropoda, pi. 10. 1876. 
Shell subturbinate, sometimes approaching a subglobose form. Spire depressed, 
or more or less elevated above the outer volution, sometimes nearly on 
the same plane; volutions three or four, rapidly expanding, the last 
extremely ventricose, with the lower part projected in the direction of 
the columella, which is much extended. Aperture subovate, broader 
above, narrowing and often extended below. 
