68 
Endoceras duplication Hall has about ten earner® in a length equal to 
the diameter of the conch. Endoceras magniventrum Hall has about 
eight earner® in a corresponding length. Endoceras angusticameratum Hall 
has between seven and eight earner® in this length. All of these species 
are of Trenton age. 
Endoceras is known also from Silurian strata, in the area west of 
Hudson bay. From the Silurian at Limestone rapids, Severn river, Ontario, 
Prof. W. A. Parks described Endoceras hudsonicum, with at least eleven 
earner® in a length equal to the diameter of the conch at the point under 
investigation. The siphuncle of this Severn River species, however, 
is relatively larger, and the septal necks do not extend down even as far 
as the septum next beneath. In a second specimen of Endoceras , found 
by Professors Savage and Tuyl in the Silurian of Severn river, the septal 
necks extend apicad for a distance of one and a half earner®. 
Whiteaves notes the presence of Endoceras or Nanno also in the Silurian 
on the portage road at the falls on Ekwan river, west of James bay. 
Phragmoceras sp. 
Plate XIV, figures 2A, B 
The specimen consists of a cast of the interior of the living chamber, 
attached laterally to matrix retaining an impression of one side of this 
living chamber and of the immediately adjacent part of the phragmacone. 
For purposes of study, the cast of the interior of the living chamber was 
broken loose from the matrix. 
Living chamber 22 mm. in height at the ventral margin of the dorsal 
lobe of the aperture; at mid-height the dorso-ventral diameter is 21 mm., 
and the lateral diameter is estimated at 20 mm. As far as may be deter- 
mined from the specimen at hand, the aperture consists of a relatively 
large, approximately circular dorsal lobe, and of a narrow, approximately 
linear intermediate slit, terminating at its ventral end in a short, spout-like 
projection. The dorsal lobe appears to be 12 mm. wide and 12 mm. long 
in a dorso-ventral direction, with a tendency toward a lessening of its 
curvature along its dorsal outline and toward an increase of curvature 
along its dorso-lateral outlines. The narrow, linear part of the aperture 
was at least 10 mm. in length. The spout-like projection at the ventral 
end of the aperture is not preserved, but its former presence is suggested by 
the curvature of the adjacent parts of the shell. Along the dorsal margin 
of the dorsal lobe of the aperture the shell is erect as in Phragmoceras , not 
incurved as in Gomphoceras. Compared with the general horizontal 
plane passing parallel to the suture at the base of the living chamber, 
both the dorsal and the ventral sides of the living chamber slope moder- 
rately but distinctly backward. The maximum lateral diameter of the 
chamber is at mid-height, and above this level the sides of the chamber 
contract so as to give its upper part a semi-globose aspect, at least toward 
its ventral side. For a distance of 2 mm. above the suture at the base of the 
living chamber, the cast of the interior of the latter is indented by the 
impression of the annular attachment ring, marked by vertical corrugations, 
of which eleven occur in a width of 10 mm. 
