ATT 
The types were not to be found in the museum at Ottawa during 
my visit to that museum several years ago. 
The young of this species increases in the transverse diameters with 
great rapidity. The ananepionic stage, Figs. 9, 10, Pl. vi, has the 
usual straight, fine striae and the metanepionic and succeeding sub- 
stages throughout the first, and a part of the second whorls have 
the costations which are common at the same age in other shells of 
this family. The umbilical perforation is of considerable size ; the 
whorls change from the rounded, cyrtoceran form of the anane- 
pionic substage, which apparently has the ventro-dorsal longer 
than the transverse diameters, very rapidly as the gyroceran stage 
approaches on the latter part of the first half of the first whorl or 
the metanepionic substage. In the paranepionic on the last half 
of the first whorl and before the whorls touch, the whorl is like the 
metanepionic volution as shown in section in Fig. 11, Pl. vi, trigo- 
nal, the venter broader than the dorsum, and the angles are rounded. 
In the ananeanic substage, after the completion of the first whorl, 
the wherl becomes digonal, with a contact furrow. Near the end 
of the first whorl, in the paranepionic substage, the ventro-dorsal 
diameter was 3 mm., roughly measured ; the transverse through the 
abdominal angles were approximately 6 mm. ; half of a volution 
beyond this, in the ananeanic substage, the transverse had become 
10 Or 11 mm., and the ventro-dorsal about 6 mm. ; less than one-half 
volution later in the paraneanic the transverse had become 16 mm. 
and the ventro-dorsal about 7 mm. ; somewhat more than one-half 
volution later, in the anephebic substage, the whorl had become 
changed to kidney shaped in section, and the septum at the base of 
the living chamber was exposed. The transverse diameter was 
29 mm., the ventro-dorsal 12 mm., both taken without the shell. 
Fig. 11, Pl. vi, shows a sectional view of the metanepionic, 
neanic and ephebic volutions. The diameters through the umbili- 
cal zone, parallel with the mesal plane, were equal or about the 
same, roughly measured, as the ventro-dorsal diameters. 
The anaphebic sutures of the septum at the base of the living 
chamber in the specimen figured has a well-marked median saddle, 
narrower than in a full-grown shell, and on either side of this were 
faintly marked ventral lobes. ‘These last were continued on the 
sides, rising steeply to the umbilical zones, where they culminated 
in broad saddles. These descended abruptly in the contact fur- 
row, forming a broad, deep, dorsal lobe. ‘These sutures are quite 
