496 MM. Foord & Crick—Shell-muscles of Celonautilus, ete. 
A drawing has also been made (Fig. EH), much reduced in size, 
from a cast of the interior of the shell of Nautilus pompiiius, in 
order that the muscular impressions of C. cariniferus might be 
compared with those of existing species. 
Fig. D represents the specimen selected for illustration, it is 
reduced in size from the original about one-half. The portion 
marked with the letters p, m, was removed from the rest of the 
shell in order that the muscular impressions might be drawn as 
seen in Figs. A and B, which are of the actual size. 
Fig. C is taken from a larger (probably adult) specimen of 
C. cariniferus (‘Sowerby Collection,’ No. 43861), and shows the 
marks of the shell-muscle on one of the angles of the whorl more 
distinctly than they can be seen on the smaller one. 
We will now describe these figures more in detail. Figure A 
represents the ventral or peripheral side of the base of the body- 
chamber. The impressions of part of the shell-muscles are seen at 
m, m, while p indicates their rugose and pitted surface, and proves 
how strongly they were attached at the angles of the whorls; this 
is further evidenced by the deep groove gr. in Figure C. 
Connecting the broader portions of the muscular impressions is a 
narrow band, near the centre of which there is a little shallow pit 
(see Figure A), which undoubtedly formed part of the muscular 
system, as the narrow band is slightly enlarged at this point to 
embrace it.’ 
Figure B is the under side of A. On this side it will be seen that 
the narrow band at its central part is strongly deflected backwards, 
in a similar manner to that of the annulus of the recent Nautilus 
(N. pompilius), so well figured (pl. xxxix. fig. 4) by Dr. W. Waagen 
in his well-known memoir entitled ‘Ueber die Ansatzstelle der 
Haftmuskeln beim Nautilus und den Ammoniden.” * 
The deflected portion bears several shallow, more or less elongated 
pits (see Figure 8), which seem to indicate a rather strong attach- 
ment of the muscles at this point, though not so strong as at the 
angles of the whorls, where the muscular impressions are broadest. 
Figure C represents the base of the body-chamber of a larger 
specimen than that from which 4 and B were drawn, and is designed 
to show more distinctly the pitted and rugose surface of the cast, 
proving, as already remarked, the strong attachment of the muscles 
at the angles of the whorl. Part of the test (¢) has been removed 
in order to expose this part of the muscular impression more com- 
pletely. 
On examining the interior of the body-chamber of the shell of the 
recent Nautilus (either N. pompilius or N. umbilicatus) two somewhat 
inconspicuous lines (Fig. /, m) are observed, enclosing a space which 
on the dorsal and ventral sides of the shell forms a narrow band,—the 
impression of the annulus,—but expands at each side into an irregularly 
oval space,—the impression of the shell-muscle,—of which the outer 
boundary is strongly arched forwards. Corresponding in direction 
1 This enlargement is not indicated in the Figure, as it should have been. 
2 Paleontographica, bd, xvii. 1870, p. 185, plates xxxix. xl. 
