AMERICAN PALEOZOIC CEPHALOPODS 
241 
24 mm. long. At the broken base the dorso-ventral diameter is 
12 mm. 
The septum at the base of the specimen curves gently dorso- 
ventrally, and curves even less laterally. The result is that the 
sutures of the septa form comparatively shallo^v lateral lobes. 
Along the dorsal side of the conch the sutures are almost directly 
transverse, but along the ventral side they rise into more or less 
distinctly angular saddles. The siphuncle is small, and is located 
less than 1 mm. from the ventral wall even along the upper part 
of the phragmacone. The number of camerae in a length equal 
to the dorso-ventral diameter in another specimen is about 8, 
and in still another specimen the segments of the siphuncle are 
seen to be narrowly fusiform. 
Figured specimens . — The originaP^^ of figures 3 a, b, on plate 3 
of the Third Report of the New York State Museum, published 
in 1850, shows the surface striae very well. These striae are 
directly transverse along the dorsal and lateral sides of the conch 
as far as the middle of the lateral sides. Ventrad of these middle 
points the transverse lines curve gradually downward until they 
meet along the median part of the ventral side at an angle of 
about 130° in the vicinity of the aperture. The hyponomic sinus 
is broadly V-shaped, and its depth equals 2 or 3 mm. Judging 
from these transverse striae, the aperture was about 15.5 mm. 
long, dorso-ventrally, 12.5 mm. wide, and had a distinctly 
angular outline at the hyponomic sinus. 
The strongly concave lengthwise curvature of the upper part 
of the dorsal outline of the living chamber in the specimens rep- 
resented by figures 6d and 6e, on the plate accompanying the 
original description, probably is due in large part to pressure, 
both specimens being preserved in a rather soft argillaceous 
limestone. 
In some specimens the cast of the interior of the phragmacone 
and of the lower half of the living chamber is marked by about 
35 faint vertical ribs, none of which correspond to any structure 
on the exterior of the shell. 
Locality and Horizon . — All of the specimens described here are 
from Middleville, New York, in the Trenton limestone. Num- 
bered 824 in the American Museum of Natural History. 
This Journal, PL XXXIX, figs. 2A, B. 
