472 
taken, is given in Fig. 31, Pl. vi. The core of the umbilical per- 
foration was exposed, the metanepionic volution is smaller and 
younger, the paranepionic section is older and is shown to be con- 
vex on the gyroceran turn or curve around the core. ‘The state of 
the section left this observation open to some doubt owing to the 
fact that it was slightly clipped on one side, exposing an older part 
of the same whorl. On wearing this same section down a shade 
farther the beginning of a dorsal furrow became apparent, and 
is given in Figs. 32, 33. 
It is, however, obvious that the dorsal furrow is very slight and it 
occurs in the usual place on thé paranepionic dorsum ; the rotundity 
and form of the metanepionic whorl was perfectly well defined. The 
umbilical perforation in this fossil was very small, and the occurence 
of a dorsal furrow at the place designated in the drawing could be 
_ accounted for as due to the contiguity of the dorsum of the grow- 
ing whorl of the paranepionic to that of the stiff wall of the 
metanepionic substage. 
The position of the siphuncle in the apex could not be deter- 
mined, but its place in the other whorls was plainly seen and 
agrees closely enough with the positions determined by Whitfield 
in the young of Lafont, with which also the characters of the 
sutures of the older whorls agreed in this specimen. 
The contact furrow is deeper relatively in the neanic stage 
than it is subsequently, when one takes into account the form of 
the whorl and the relative extent of the sides covered by involu- 
tion. It is, however, very well marked in all stages, and its disap- 
pearance upon the latter part of the last whorl, as has been shown 
in Whitfield’s figures and those given in this paper, is a significant 
and instructive fact that has been discussed in other parts of this 
essay. The aperture of Fig. 7, Pl. vii, was removable, and this 
being taken off the last vestige of the impressed zone is seen on 
the dorsal side of the free whorl in the front view of the same 
specimen, Fig. 8. The portion removed is so short that it is pos- 
sible it may represent the rim of the aperture itself. 
The sutures of the anephebic stages differ considerably from 
those of the adult, being straighter and more like those of Trocho- 
lites, and it may be questioned whether this should not be called 
the paraneanic substage on account of its close resemblances to 
Trocholites. 
In the full-grown shell of the parephebic and gerontic age, as 
