250 
PALAEONTOLOGY OF NEW YORK. 
Siphuncle small, slightly excentric. Its character in its passage between 
the septa has not been observed. 
The organic deposit consists of an areola on the septa, surrounding the 
siphon, from which in some specimens there are obscure, radiating, vascular 
ridges. On the exterior walls of the air-chambers in the cast, and indicat¬ 
ing the ventral side, there is a longitudinal raised line or keel, represented 
in fig. 4, pi. 78 A. The other specimens also show this line, but it is not 
represented in the figures. Sometimes the line is made more prominent 
by a distinct, shallow groove on either side. 
The test is usually so far dissolved, or otherwise removed, that no evi¬ 
dence as to its thickness remains. Several of the specimens preserve traces 
of the surface-markings, which consist of fine and closely arranged sharp, 
transverse striae, crossed by very fine, longitudinal striae. The transverse 
striae curve backward over the dorsal and ventral sides, and forward over 
the lateral portions of the shell. 
No entire individuals of the species have been observed. One specimen 
has a length of 260 mm. Others measure about 250 mm. in length, and are 
incomplete towards the apex, and we may infer that they have been at least 
100 mm. longer. The greatest diameter in incomplete specimens is less 
than forty mm. 
This species bears some resemblance to special conditions of O. luxum, but 
may be distinguished by the excentric siphuncle, and absence of the conspicuous 
organic deposit. O. inoptatum, pi. 37, fig. 1, is of similar form and proportions, 
but differs in having a very excentric siphuncle, and no evidences of an areola 
on the septa. 
This species is unknown to me in any formation except the Schoharie grit. 
Formation and localities. In the Schoharie grit at Schoharie, and in the 
Ilelderberg mountains; but is unknown beyond the limits of this formation in 
the eastern part of the State of New York. 
