170 
PALAEONTOLOGY OF NEW YORK. 
except the annulations which are subcrystalline; but when occurring in 
calcareous beds, the entire test is quite crystalline throughout. 
This fossil has usually a length of from fifteen to twenty or twenty-two mm., 
while a single specimen, with the apex imperfect, measures thirty-one mm.: 
the largest individuals have a diameter at the mouth of nearly three mm. 
(the'figures are enlarged to three diameters). Under ordinary observation the 
specimens present the appearance of a more abrupt increbescence of the 
annulations at about one-third the distance from the apex. Interruptions in 
the growth have sometimes increased or diminished the space between the 
annulations, as shown in figure 16 at a little above the middle of its length, and 
sometimes one or two of the annulations near the aperture are smaller than 
those preceding or following. 
This species differs from the T. scalariformis in its more slender character 
and extremely attenuate apex with finer annulations: also upon the body of the 
shell the annulations are more prominent and acute, while the intermediate 
striae are fewer. In its general character it resembles the T. elongatus of 
the Lower Helderberg group ; but the annulations are proportionally stronger, 
a little n\ore closely arranged, and not covered by the striae as in that species. 
Formation and localities. In the calcareous shales of the upper part of the 
Hamilton group, at Pornpey Hill in Onondaga county, at Cayuga and Canan¬ 
daigua lakes, at Bellona in Yates county, and at Geneseo, N. Y. 
Tentaculites attenuates. 
PLATE XXXI, FIGS. 19, 20. 
Tentaculites attenuatus, Hall. Illustrations of Devonian Fossils: Pteropoda, pi. 2G, figs. 19 and 20. 1S76. 
Form elongate-conical, regularly expanding from the apex, and with no 
evidence of becoming cylindrical towards the aperture. The apical 
portion of the shell is very finely marked by acute annulations for a 
distance of about two and a half millimetres, without visible intermediate 
strial. Beyond this, towards the aperture, the annulations increase in 
distance, and the intermediate furrows are marked with one, two, three 
