170 PA LJEONTOL 00 Y OF NE W YORK. 



•pt the cumulations 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 more 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 

 Samiltoo group, at Pompey Hill in Onondaga county, at Cayuga and Canan- 

 daigua lakes, at Bellona in Yates county, and at Geneseo, N. Y. 



Tentaculites attenuatus, 



PLATE XXXI, FIGS. 19, 20. 

 trulUes attenuatus, Hall. Illustrations of Devonian Fossils: Pteropoda, pi. 20, figs. 19 and 20. 1876. 



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 

 striae. Beyond this, towards the aperture, the annulations increase in 

 distance, and the intermediate furrows are marked with one, two, three 



