168 
PALAEONTOLOGY OF NEW YORK. 
The specimens attain the length of one inch, rarely more, and usually 
somewhat less. The longest one observed has a length of nearly one inch and 
a quarter. 
This form is stronger and more robust than any of the species of the 
Hamilton and Chemung groups. It differs from the T. bellulus in having the 
annulations of the distal portion more obtuse, while, in the Hamilton species, 
the ajDical portion with fine annulations is proportionally longer and more 
attenuate, and the entire length in the longest individual is greater. In T. 
bellulus the annulations on the large part of the tube are more acute, the 
intermediate depressions are proportionally wider, and the transverse striae 
somewhat stronger. T. scalar if or mis differs in the same manner from T. elon- 
gatus of the Lower Helderberg group, which has thin, sharp annulations, and 
a more gradually attenuate form. 
In the usually macerated condition of most of the specimens, the transverse 
striae are chiefly obliterated, and it is only in rare individuals that these 
markings are well preserved. The same influence has subdued the sharpness 
of the annulations, and in many examples this cause, together with the effects 
of subsequent pressure, has given them a subnodose character. 
In the compact limestones of New York and of Sandusky, Ohio, the exterior 
surface is rarely well preserved, and it is only on some slabs of a thinly 
laminated and often argillaceous limestone that the full form and external 
characters have been retained. 
Formation and localities. This species occurs in the Upper Helderberg lime¬ 
stone at Schoharie in eastern New York, and at Le Hoy and other points in 
the central part of the State. It is abundant in the same limestone near 
Sandusky and at Delaware, Ohio, and at Charlestown, Ind. It likewise occurs 
as casts of the interior, or sometimes partially preserving the shell, in a sand¬ 
stone at the base of the Corniferous limestone at Pendleton, Indiana. The 
known geographical extension of the species is therefore at least seven hundred 
miles, and it. seems quite probable that it will prove coextensive with the 
limestone formation of the Upper Helderberg group. 
