246 PALAEONTOLOGY OF NEW YORK. 



forms an irregular, sharply-furrowed 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 



