AMERICAN PALEOZOIC CEPHALOPODS 
233 
minated both at top and bottom by a septum. Specimen 1281b 
is smaller, but shows a similar lengthwise curvature. Specimen 
1281e shows the apical end. (Specimen 1281 is described here 
as Tripteroceras pauquettense, and does not properly belong to 
the type series of Orthoceras hdstatum.) 
The conch of specimen 1281d, here figured, enlarges with a 
lateral apical angle of 20°. The ventral side is strongly flattened. 
The dorsal side shows a slight tendency toward angularity 
along its median line. From this median line toward the lateral 
angles, the dorso-lateral sides are slightly flattened. The lateral 
angles are abruptly rounded. Toward the apical end, the speci- 
men is gently curved lengthwise. The sutures of the septa curve 
evenly downward on both the dorsal and the ventral sides. The 
siphuncle is close to the ventral side, but its structure is un- 
known. The lines of growth are almost directly transverse 
around the entire specimen, but on the ventral side their direc- 
tion is very slightly concave upward, and on the dorsal side 
there is a corresponding but almost imperceptible concave curva- 
ture which is interrupted medially by an almost imperceptible 
convex curvature. 
31. TRIPTEROCERAS PAUQUETTENSE SP. NOV. 
PLATE XXXI, FIGS. 2A, B, C, D 
Orthoceracone strongly compressed ; at its upper end the 
lateral diameter is 24 mm. and the dorso-lateral one is 15 mm. 
The cross-section is slightly subtriangular, owing to the smaller 
convexity of the ventral side. The dorsal side is quite regularly 
rounded and forms about two-fifths of a circle having a radius 
of 13 mm., while the ventral side forms about one-fifth of a 
circle having a radius of 20 mm. The lateral margins are rap- 
idly rounded. The center of the siphuncle is 4 mm. from the 
ventral wall. It enlarges from a diameter of 4 mm. at the septa 
to 5 mm. at mid-height within the camerae. Its passage through 
the septum is 1.5 mm. in diameter. 
The specimen is 25 mm. in length. Six camerae occur in a 
length of 24 mm. On the ventral side of the conch, the sutures 
of the septa curve strongly downward toward the median line, 
but, on approaching the lateral outline of the conch, this curva- 
ture of the sutures becomes slightly convex. Along the median 
line of the ventral side the downward curvature of the sutures 
