455. 
ceras (Pl. vi, Fig. 5) with the figure of the young of Pycnoceras 
apertum (Pl. v, Fig. 18). The nepionic stage has rounded dorsum 
and more ‘rounded venter than appears in the Fig. 19, Pl. vi, be- 
cause of the presence of a thick band of shell on the venter, con- 
sisting of its own shell which is not present on the sides and also 
of the corresponding part of the shell of the dorsum of the next 
older whorl that has been broken away. A slight contact furrow 
is present at the beginning of the ananeanic substage when the whorls 
come in contact at the point indicated in Fig. 18 by the end of the 
outline of the restored apex. This zone is further shown by the 
band of shell left on the venter from the dorsum of the next older 
whorl, which was the neanic volution. Upon this, also, there are 
remnants of the septa of this stage, showing that this zone was 
immediately accompanied by the advent of dorsal lobes in the 
sutures. These replaced the dorsal saddles of the nepionic stage. 
In the ephebic stage the siphuncle assumed a propioextraventran 
position and retained this until the gerontic stage. 
The form of the whorl remains quite similar, the ventro-dorsal 
diameters being longer than the transverse, but the venter becomes 
broader in proportion than the dorsum in neanic and ephebic 
stages. 
In the gerontic stage the living chamber and part of the septate 
last whorl alone are free in some species, in others the age at which 
the whorl becomes free varies greatly. 
The type of the genus is the young specimen, Fig. 18, which 
shows that the young are distinct from those of Tarphyceras, being 
much less closely coiled and having distinct form of whorl and 
large umbilical perforation. 
There are several undescribed species of this genus in the fauna 
of Newfoundland. 
PYCNOCERAS APERTUM, n. Ss. Pl. v, Figs. 18-20. 
Loc., Port au Port, Newfoundland. 
This single specimen was found in the dolomitic limestone or 
calciferous in company with the closer coiled young of Tarphyceras. 
The nepionic stage is prolonged and _ has the oval form of whorl 
and sutures of the adults of the cyrtoceran genus, Melonoceras, and 
of the nepionic and neanic stages of the gyroceran form, Apheto- 
ceras, its nearest affine, which occurs, however, later in the fauna 
of the Quebec group. 
