AMERICAN PALEOZOIC CEPHALOPODS 
211 
their basal part curves outward where joining the top of the 
septal neck immediately beneath. The apical end of an endo- 
siphocone traverses the greater part of the length of this speci- 
men ; it is almost in contact with the ventral wall of the siphuncle. 
The diameter of the siphuncle is estimated at 30 mm. and that of 
the conch at 58 mm., but in neither case is more than the ven- 
tral side actually exposed. Five camerae occur in a length equal 
to the diameter of the conch. The apical angle appears to be 
larger than 3°, but the specimen is not suitable for the accurate 
measurement of this angle. 
The specimen^® represented by Hall’s Figures lb and Ic on Plate 
43 exposes 12 camerae in a length of 106 mm. Near the base of 
the specimen 7 camerae occur in a length equal to the diameter of 
the conch ; near its upper end 6 camerae occur in a corresponding 
length. At mid-length the diameter of the specimen is 56 mm. 
Here the concavity of the septa is 15 mm. The diameter of the 
siphuncle at the top of the specimen is 26 mm. If the siphuncle 
was not in actual contact with the ventral wall of the conch, it 
was at least very close to the latter. About 30 mm. below the top 
of the specimen an endosiphocone starts downward, and 80 mm. 
farther down its cross-section is seen at a distance of 1 mm. from 
contact with the dorsal side of the siphuncle. Here its lateral 
diameter is 15 mm., and its apical angle is approximately 7° or 8°. 
The apical angle of the conch probably did not exceed 3°. 
Figure Id on Plate 49 of Hall’s monograph represents a speci- 
men with more numerous camerae than usual. The upper end of 
an endosiphocone is exposed. 
Figure le on plate 49 represents chiefly an endosiphocone^® 
with an apical angle of about 8°. It is badly bent at mid-length, 
and retains there part of the camerate portion of the conch, 
poorly preserved. 
While endosiphocones with apical angles of 9° or 10° are most 
common, occasional specimens with angles distinctly lower or 
higher also occur. 
Locality and Formation. — Middleville, New York, in the Tren- 
ton limestone. 
Specimens, with one exception, all numbered 809-1. The 
originals of fig. 4 on plate 48 and figs, la, lb, Ic, le on plate 49 
are in the American Museum of Natural History. Fig. Id on 
PL 21, fig. 3; pi. 23, fig. 1, of this Journal. 
PI. 22, fig. 3; pi. 23, fig. 3; pi. 25, fig. 2, of this Journal. 
