158 
NATJTILOIDEA. 
I have nothing to add to Dr. Waageu’s very exact description of 
this species, hut there is one thing in his figure to which exception 
must he taken, and that is, that it represents the ribs as being 
equally well developed upon all parts of the shell. On looking at 
the type specimen, however, it is seen that the ribs, though strongly 
developed upon the cast of the first whorl and about half of the 
succeeding one, become obsolete upon the last half-whorl, including 
a small j)ortioii of body-chamber. This seems to be the case 
also in the British Museum example, so far as its eroded surface 
enables one to judge. 
A portion of the test is preserved upon the specimen from the 
Calcutta Museum. It is nearly 2 lines in thickness, increasing to 
3 lines on the ribs. The specimen is crushed out of shape, one side 
of the periphery being forced beyond the plane of the other side, 
causing the umbilicus to be deeper on one side than on the other. 
Dr. Waagen’s figure represents a much more perfect specimen 
than the original proved to be, having been “ restored ” to such an 
extent as to make it quite unrecognizable as a picture of the type 
specimen. Perhaps his figure was intended rather to represent the 
aggregate characters of the species than the features of the indivi- 
dual upon which it was founded. It is, however, a matter of some 
consequence that “ type” specimens should be faithfully drawn, so 
that in case of any difficulty arising as to the identity of a species, 
reference may be made to the original figure as a trustworthy sub- 
stitute for the specimen itself. 
Many type specimens belonging to collections of historical interest 
have failed to be identified in consequence of the restoration of the 
figures representing them. This is the case, for example, with 
some of the figures in the ‘ Mineral Conchology,’ and also in some of 
those of the fossils collected by Darwin in the ‘Voyage of the 
‘ Beagle 
The British Museum example is a very large cast, much weathered 
and broken, but showing on one side nearly the whole of the septate 
part of the shell and a small portion of the body- chamber, with the 
very deep umbilicus and remains of the tubercular ridges, which 
are about as numerous as j^he septa. About 32 septa may be 
counted on the last volution, which is the number estimated by 
Dr. Waagen upon his specimen. The last two septa are 4 lines 
apart upon the edge of the umbilicus, the others about 5. The 
following are the principal dimensions of the specimen : — greatest 
diameter of the shell 9 inches ; greatest diameter of umbilicus 3| 
inches ; greatest height of whorl (ventro-dorsally) 4 inches ; greatest 
breadth of the same 5| inches. 
