NAUTILLD^. 
319 
animal, probably an enlargement of the epithelial cincture. It was 
on this character that De Montfort, mistaking the depression for the 
mouth of a second siphuucle, founded his genus Bisipliites. The 
siphuncle is small and excentric. The lines of growth, like those 
of the preceding species, are decussated, and reflected backwards in 
broad undulations.” {Edwards.) 
liemarks. There is a notable discrepancy between J. Sow- 
erby’s description and figure of this species and those of J. de 
C. Sowerby and F. E. Edwards. J. Sowerby’s description runs 
thus : — “ Gibbose, plain, not urabilicate ; front flattish : sides con- 
vex ; aperture rather wider than long.” Sowerby continues : — 
“ The volutions of this Xautilus increase rather more rapidly in size 
than those of X. imperialis, which is near akin to it, and from 
which it is further distinguished by the solid columella or axis, by 
the convex, not straight, sides of the aperture or section in the 
young shells, and the expanded sides and straight front of the 
aperture in the adult ... I have named it regalis, as it seems 
little inferior in splendour to the imperialis, and nearly equals it in 
size, though it appears from two or three specimens I have with 
small remains of the thickened edge of the aperture near the axis, 
that it is full-grown when about nine inches in diameter and five 
in thickness.” 
It will be observed that J. Sowerby in his description of N. regalis 
describes his shell as having the “ sides convex,” and the “ aperture 
rather wider than long,” and this is expressed in his figures 
(pi. ccclv.) ; but in the descriptions and figures of this species given 
by J. de C. Sowerby and E. E. Edwards no such impression of the 
form of the shell is conveyed ; on the contrary, J. de C. Sowerby’s 
figure represents a shell with flattened sides and an aperture which 
is higher than wide, and Edwards’s description and figures lead to 
the same conclusion as to the shape of the shell, the aperture of 
which he says “ presents a subquadi’ate appearance,” and the shell 
is “ flattened on the sides.” As it would be impossible to recon- 
cile these divergent descriptions, it becomes a question whether 
J. Sowerby’s name regalis can be retained, especially as his type 
specimen is not to be found. I have thought it best, however, to 
retain the name for the species figured by J. de C. Sowerby, who 
was very probably acquainted with J. Sowerby’s figured specimen. 
Edwards’s figures and description fully supplement those of J. de 
C. Sowerby, and they manifestly refer to a similar species, of which 
there are numerous examples in the British Museum. This affords 
another instance of the difficulty of recognizing species from fore- 
shortened figures. 
