124 
PALEONTOLOGY OF NEW YORK. 
the shell 'carinate, and the casts obtusely but distinctly angular on the dor¬ 
sum ; apparently not sinuate or but slightly undulated on the anterior 
margin. 
Surface marked by regular, sharply elevated, subparallel, transverse stria 1 , 
which are comparatively distant (at least twice or thrice their width) near 
the apex and on the upper part of the outer volution, but become more 
crowded towards the front of the shell. On the upper part and sides of 
the shell the intermediate spaces are regularly cancellated by short revolv¬ 
ing strife which hardly rise so high as the transverse ones, giving the 
entire surface a pitted or finely reticulate character, similar to that repre¬ 
sented in fig. 28. Approaching the margin, the spaces between these 
strife diminish, as the result of the rate of growth in the shell, and they 
often become so crowded as to present the character of simple undulating 
granulose lines of growth. These strife are not sensibly curved in passing- 
over the rounded carina. When the shell is jmrtially exfoliated they 
give a lamellose-striate character to the surface. 
The fossil is usually found in the condition of casts of the interior, which 
preserve some marks of the transverse strim, but the exterior shell is rarely 
seen. The dorsum is decidedly carinate in one specimen where the shell is 
• 
preserved, and the casts are always distinctly angular,* and sometimes subcari- 
nate, along the dorsal band. The transverse strife are extremely irregular in 
their distance from each other, becoming crowded as the rate of growth is 
impeded. This condition gives to the reticulate character considerable varia¬ 
tion in the size and proportion of the depressed spaces between the two sets of 
strife. At the time of writing the original description I had not seen the entire 
shell-surface, and it was supposed to be without revolving strife. 
In comparison with specimens recognized as C. pileolus, the dorsum is more 
distinctly angular, and when entire is carinate, while in a single specimen of 
that species which retains the shell, or at least where the surface-markings are 
fairly preserved, the dorsum is angular but not absolutely carinate (see fig. 29 
of plate 25). The specimen fig. 22 of the same plate is a cast of the interior, 
somewhat less laterally expanded than usual—erroneously represented as 
