MM. Foord & Crick—Shell-muscles of Colonautilus, ete. 495 
Museum (Nat. Hist.), some were found to exhibit upon the cast of 
the body-chamber distinct marks of the shell-muscles. In one 
specimen (No. 50190) these are so perfect as to give a very clear 
outline of their form, and some of the test having been removed, 
their entire course can be made out. 
The accompanying Figures (A, B, D) show the appearance of these 
muscular impressions, carefully drawn of the natural size, from this 
specimen. 
mel 
i) | 
Celonautilus cariniferus, J. de C. Sowerby, sp., from the Carboniferous Limestone, 
Cork, Ireland. —4, ventral or peripheral aspect of the base of the body-chamber 
(nat. size), showing at m, m, marks of the shell-muscles (m in all the other figures 
has the same meaning) ; y, in all the figures (exclusive of ¢) refers to the pitted 
and rugose surface of the muscular impressions: B, dorsal (internal) aspect of the 
same fragment, ¢, test, 27, dorsal lobe of a septum: C, base of the body-chamber 
of a larger (? adult) specimen, ¢, test, gr, groove: D, reduced figure of a nearly 
perfect example of this species, from which the fragment lettered 4 and B was 
removed, as explained elsewhere in the text: , outline, much reduced in size, 
drawn from a cast of the interior of Nautilus pompilius ; t, finely impressed lines 
left by the shell-muscle, s, sutures of the septa. 
was used by Hackel for a genus of Radiolarians. The name Trematoceras proposed 
by Hyatt (Proc. Boston Soc. Nat. Hist. 1883, vol. xxii. footnote, p. 291) in lieu of 
Trematodiscus is equally ineligible, because preoccupied, for although the species 
described by Hichwald (Leth. Rossica, 1860, vol. i. p. 1259)—Trematoceras discors 
—was a Bactrites, a generic name once published cannot be again employed, even 
for a different group, without risk of confusion. 
