228 ARTHUR WILLEY. 
Finally, in a third variety the deposition of callus will have 
been entirely left out and the whorls loosely coiled, so that we 
shall have the above-mentioned shoulder, a perforated um- 
bilicus, and visible whorls. 
The latter variety is not identical with the so-called N. 
stenomphalus, but is, in a sense, intermediate between the 
latter and N. umbilicatus. I obtained a single example 
from New Guinea waters, kindly given to me by the Hon. M. 
H. Moreton, of Government House, Samarai, British New 
Guinea. I have pleasure in naming it N. pompilius, var. 
Moretoni. 
In acollection of shells of N. pompilius it may be ob- 
served that the extent of deposition of callus over the um- 
bilicus is very unequal; and that while there is usually a thick 
prominent plug of white callus, sometimes the deposition of 
the latter has been so deficient as to leave a deep umbilical 
depression on cither side. 
A peculiar feature about the variations now being dealt with 
is that they may occur on one side of the shell only, the other 
side being more or less normal. 
Pl. 13, fig. 7, represents the umbilical region of a variety of 
N. pompilius, whose umbilicus was only partially perforated. 
On the right side of the shell (the latter being considered with 
the convex side downwards, as it is in the fresh condition) 
there was a deep hole, about a centimetre in depth; on the 
other side there was a deep umbilical depression, which, how- 
ever, was closed over with callus, with the exception of a 
minute pin-hole aperture—perhaps half a centimetre in depth. 
This latter could only be made out by close inspection, and 
at first sight the Jeft side of this shell appeared to be practi- 
cally normal. 
It is clear that if this variation were carried a little farther 
in the same direction, we should have a form possessing the 
essential features of N. stenomphalus, and there is no 
reason at present to regard the latter as anything more than a 
variety of N. pompilius with a persistent perforated um- 
bilicus. In a specimen of N. stenomphalus in the Austra- 
