12 4 PALEONTOLOGY OF NEW YORK. 



tlu' 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-. 

 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 striae 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 

 stria; 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 striae are not sensibly curved in passing- 

 over the rounded carina. When the shell is partially 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 striae, 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 striae 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 

 striae. At the time of writing the original description I had not seen the entire 

 shell-surface, and it was supposed to be without revolving stria-. 



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, 2fl 

 of plate 2-">). The specimen fig. 22 of the same plate is a cast of the interior, 

 somewhat less laterally expanded than usual — erroneously represented as 



