PTEROPODA. 
167 
Tentaculites scalariformis. 
PLATE XXXI, FIGS. 3-11. 
Tentaculites scalaris , Hall. Geology of N. Y. Surv. Fourth Geolog. Dist., pp. 172, 173, fig-. 2. 1843. 
Not T. scalaris, Schlotheim. Silurian Researches, p. G43, pi. 19, fig. 16. 
T. scalariformis and T. sicula. Hall. Illustrations of Devonian Fossils : Pteropoda. pi. 26, figs. 3-11. 1876. 
Form elongate-conical, straight, somewhat more cylindrical in approaching the 
aperture; with the apex, in well-preserved specimens, extremely attenuate, 
and quite solid for one-fourth to one-third of the entire length of the 
shell. Annulations prominent, subangular, sometimes rounded on the 
larger part of the cone; closely arranged and sharply angular near the 
apex, gradually increasing their distance, becoming less angular with 
the increase of the size of the shell, and obtuse and rounded towards the 
aperture; usually but little variation in character on the outer half of 
the length, where the spaces between are greater than the annulations. 
Interspaces and annulations, when well preserved, marked by fine, even, 
transverse striee, of which nine or ten may be counted in the furrows, 
and half as many on the summit and sides of the annulations. 
In a few specimens there is much irregularity in the distance and develop¬ 
ment of the annulations towards the aperture. The extreme point of the apex 
is rarely or never preserved in our specimens; but measuring the annulations 
at the smaller extremity we find that the distance between them increases 
according to the following figures: taking the measure of the first nine annula¬ 
tions in four specimens, we have the following ratio: (1) 9, 5, 3,3,3; (2) 9, 
5, 4, 4, 3; (3) 9, 5, 4, 3, 4^; (4) 9, 5, 4, 3, 2-h, 2, 2. The fossils are imbedded 
in compact limestone, or spread over the laminated surfaces of the semi- 
argillaceous layers, and the specimens, with rare exceptions, are compressed 
and often extremely flattened, except the apical portion, which is solid and 
preserves its form. The degree of compression influences the form of the cone, 
as may be seen in the figures. In a few well-preserved specimens, the cylin¬ 
drical character of the tube towards the aperture is scarcely noticeable, and 
the whole appears as an elongated cone. 
