PTEROPODA. 
175 
Otsego county, both in the shale and in limestone nodules, and is abundant in 
the upper part of the shale near Alden, in Erie county. It also occurs in the 
soft shales of the Hamilton group on Canandaigua lake. 
STYLIOLA, Lesueur (1826). 
CRESE1S, Rang (1829). 
Styliola, Lesueur, Ludwig - , Richter, Hall. 
In 1864, Prof. Rudolph Ludwig (Palaontograpliica XI) proposed to restrict the 
generic term Tentaculites to the annulated forms, in accordance with the 
o 
original definition of the genus; and placed under the genus Styliola, of Le¬ 
sueur, all the smooth forms, or those which are either longitudinally or 
transversely striated, but without annulations. 
In 1865, 1866 and 1867, Dr. R. Richter ( Zeitschrift der Dcutsch. Geol. Gesell- 
schaft ) adopted the same distinction among these fossil forms heretofore referred 
to the genus Tentaculites. 
In 1867, M. J. Barrande has maintained the same view, and described 
Styliola clavulus, from the Bohemian strata of Devonian age, in his Systeme 
Silurien du Centre de la Boheme. 
A/, AA. AA AA. A/* AA AI* AA A^ A£* A^ A^ 
-TV '/V -TV 'A' 'A' "TV '7V *7V 'A' -TV 'A' "A" 
The following definition of the genus, as given by Prof. Ludwig, is translated 
from the work of M. Barrande : 
Generic characters: “ Shell small; transverse section circular ; closed below, 
and thicker than in the upper part; conical. Surface without annulations, 
smooth, but with fine striae of growth, and sometimes with fine longitudinal 
striae; without longitudinal slit, but sometimes with one or two longitudinal 
grooves, which do not penetrate the shell; without operculum, and without 
interior partitions, but having a persistent point, sometimes curved backward. 
The greatest width is at the opening, which is oblique or normal to s the axis of 
the shell.” 
This definition of the genus, applied to the American forms known to us, 
renders the distinction between Tentaculites and Styliola sufficiently clear. 
M. Barrande has remarked, with much reason, that from the nature of these 
