246 
PALEONTOLOGY OF NEW YORK. 
forms an irregular, sharply-farrowed cylinder with the sides concave between 
the septa. This filling is deposited to such an extent in some individuals as 
to nearly fill the cavity of the chambers. Figure 13, pi. 81, represents this 
phase. The pitted or eroded appearance is carried, not only over the septa, 
but over the deposit around the siphuncle, and occasionally over the walls of 
the chambers, figs. 12-14, pi. 112. 
All the better specimens of the interior casts observed, show a deposit 
along the middle of the ventral side of the chamber walls, adjacent to a nar¬ 
row carina, which indicates the existence of a groove upon the interior sur¬ 
face of the original shell, and through which a communication may have 
been continued between the interseptal spaces, successively, as the animal 
has advanced its chamber of habitation. An evidence of this is furnished 
by the fact that the carina is always more prominent at the anterior portion 
of each chamber, where it penetrates the margin of the septum. The func¬ 
tional connection of this feature with the organic deposit around the 
siphuncle is indicated by its presence in species where the deposit is very 
* 
marked, as in the present form. This connection is generally preserved as a 
longitudinal raised line or carina; but the specimens figured on plate 35, 
figures 5 and 6, show a variation from a simple line to a complex deposit, 
having a somewhat symmetrical form, arranged in straight or curving lines 
on both sides of the central carina; and the latter, with these accessory 
depositions in other portions of the tube, assuming the form of oval or 
rounded nodes. This feature upon the inner walls of the shell is visibly a 
continuation from the areola which surrounds the siphuncle, and its 
extension on one side, which is continued to the margins of the septa and 
along the ventral walls of the chambers. 
This species is the most common and characteristic one found in the Scho¬ 
harie grit. The external shell was probably very thin, rendering the tube 
liable to the great degree of compression and distortion which is exhibited by 
the majority of specimens. Frequently the chambers are oblique to the axis, 
and displaced, as shown in fig. 4, pi. 35, and figs. 3, 7, pi. 77. The siphuncle 
has rarely been preserved. Only one of the numerous sections made, affords 
