571 
before the retroversal gerontic stage begins. The apex does not 
exhibit any indications that the species had an excentric young 
stage even at the small diameter of 5 mm. in one specimen. ‘There 
appear to be no tubercles on the earliest whorls examined, probably 
the-neanic stage. Two irregular rows of tubercles are introduced in 
the ephebic stage with alternating untuberculated coste. The 
tuberculated cost are sometimes bifurcated, and sometimes single. 
The coste are closely set, subactite ridges, with concave flutes 
between them both, arching apically, the flutings broader than the 
costal ridges, but the surface is otherwise smooth. 
The height of the coil is over 40 mm. in the largest specimen, 
through the ephebic whorls, although the apex is imperfect. In two 
other specimens this length is much less, although the number of 
the whorls is about the same. The diameter of this specimen 
through the parephebic whorl is 34 mm. The height (transverse 
diameter) of the parephebic substage is 19 mm., the ventro-dorsal 
diameter about 13 mm. ‘The diameter of the umbilical opening 
must have been less than 12 mm. 
The costz are wider apart in the last of the ephebic stage, or par- 
ephebic substage, and I expected to find that they died out altogether 
for a certain space, but there was no evidence of this. They, how- 
ever, appear to be slightly more prominent on the gerontic volution 
than on the parephebic substage. 
The contact furrow begins early, being present on the smallest 
whorl examined. There is therefore no positive indications that 
this species had uncoiled or excentric young as in Emperoceras. 
In the anagerontic substage the whorl bends downwards or orally 
in two dextral specimens, and in the metagerontic acquires larger 
tubercles and coarser coste, sometimes bifurcated, and bends 
upwards towards the base of the ephebic volution, forming the 
retroversal living chamber. The last part of this, or the parage- 
rontic substage, is nearly or quite straight, the bifurcations disappear, 
leaving the coste straight, and the tubercles also gradually disap- 
pear. The latest senile substage is also nearly if not quite bilaterally 
symmetrical and strongly contrasts in this respect with all the stages 
preceding the metagerontic substage. The return to the symmet- 
rical form of whorl really begins in the metagerontic substage. The 
living chamber has an aperture in one specimen. ‘This is straight 
across the venter, has slight crests on the sides, and is straight or 
with very slight crest on the dorsum. 
