CEPHALOPODA. 793 
Triptoceras sp.] 
representing pretty much the entire body-chamber. Its dimensions are 21 by 9 mm. 
The distal extremity which exposes a septum is 10 by 5 mm. 
This species is readily distinguished by its distinct arcuation, rapidly expanding 
shell and the great difference in the convexity of the sides, 
Formation and locality.—In the Trenton limestone, Cannon Falls, Minnesota. W. H. Scofield. 
TRIPTOCERAS sp. ? 
There is a single specimen, an internal cast of the deep body-chamber, bearing 
a septum at is distal extremity, which presents differences from any of the foregoing 
species. The convexity of the septa and sides is about the same as that of T. 
planoconvexum but the inclination of the lateral margins is greater, with the sides 
acutely angled and almost carinate. The body-chamber, also, is distinctly arcuate. 
It nearest relations are with this species, as it is decidedly less convex and less 
rapidly tapering than 7. oweni. ‘The single specimen is from the Galena horizon 
near Cannon Falls, Minnesota. 
Billings described two species of this genus from the Trenton series, viz.: 
Orthoceras ziphias*, and O. hastatwm;. In the absence of illustration it is difficult, 
from the not very precise descriptions, to establish their specific traits. The former, 
T. ziphias, appears to have the lateral angles obtuse, in which respect it is unlike 
T. planoconvexum; its convexity is less, its size and apical angle much greater than 
in T’. oweni, while its lateral margins are less blunt and its venter less flat than 
in T. planodorsatum. In T. hastatum the lateral angles must be even more obtuse 
than in 7’. planodorsatum, the shell also tapering more rapidly and the septa being 
more convex. 
The Orthoceras servile Billings}, from the Quebec group, is a Triptoceras with 
rapidly tapering margins and rather convex sides. 
TRIPTOCERAS LAMBI Whiteaves, 1891. 
PLATE LVI, FIGS. 1 and2. 
Gonioceras lambi WHITEAYES, 1891. The Orthoceratide of the Trenton limestone of the Winnipeg 
Basin; Trans. Royal Soc. Canada, vol. ix, sect. iv, p. 86, pl. X1, figs. la—-b. 
Shell large, biconvex and lenticular in transverse section. Convexity of the 
sides subequal, that of the dorsal side being slightly the greater. Ventral side 
slightly flattened medially. Dorsal and ventral lobes broad and regularly convex, 
deeper on the dorsum, the general convexity being more decided than in the other 
species here noticed. Saddles acute, more distinctly so as viewed from the ventral 
* Rept. Geol. Surv. Canada, for the year 1856, p. 318. 1857. 
+ Op. cit., p. 333. 
+ Palwozoic Fossils, vol. i, p. 252. 1865. 
