14 
Prof. R. Owen on the Anatomy 
paragraph on the Spirula is “ En zit aan de klippen ”* . 
Admitting this function of the terminal suctorial disk, which 
is peculiar to Spirula among Cephalopods, yet it nevertheless 
occasionally floats, and probably passes more of its time as a 
swimmer than does the Nautilus. Rumphius observed both 
multiloculars on the shores or coast of Amboyna. The sub¬ 
ject of the present supplementary monograph, and that of J. 
E. Gray and Lovell Reeve, was captured, recent if not 
living, on the shore of New Zealand. A Spirula, borne away 
from its shores by storms or currents, would find subsistence 
in the open ocean as long as nutriment could be taken by its 
prehensile organs. In regard to its relations to Nautilus I 
would submit the following remarks. 
The more or less fixed attachment of a muscle being 
regarded in anatomy as its “ origin,” the chief masses of the 
muscular system in both Nautilus and Spirula have a similar 
origin, viz. the terminal open chamber of the multilocular 
shell. In Nautilus the retraetores infundibuli and retractores 
capitis arise on each side of the inner surface of that chamber 
by a single origin f, the insertional tissue or “ tendon ” of 
which, however, is continued round the circumference of the 
chamber at the level or line of the main parial attachments. 
In Spirula the corresponding muscular masses arise equally 
from the entire circumference of the terminal part of the 
inner surface of the last chamber, but also extend their at¬ 
tachments over the margin and a little way beyond it on the 
exterior of the shell; they are, in fact, “ shell-muscles ” in 
the same sense as those so-called in Nautilus. In both 
genera, therefore, the shell, besides other offices, serves as 
the point cVappui of the retractors of the funnel and of the 
head with its locomotive and prehensile organs. Moreover 
the last chamber of the shell in Spirula also receives part 
of the visceral mass, viz. the hind termination of the liver, 
which, covered by its capsule, and this again by the peritoneum 
or a delicate aponeurosis continued from the attached shell- 
muscles, constitutes the hemispheric mass that fills the 
chamber and forms or sends off the beginning of the membra¬ 
nous siphon. This siphoniferous and visceral mass (“calotte” 
of De Blainville J) is answerable in Spirula to the siphoni¬ 
ferous and visceral mass which, in Nautilus , occupies the 
* ‘ D’Amboinsche Rariteitkamer,’ fol. 1741, p. 61. 
f ‘Memoir on the Pearly Nautilus,’ 4to, 1832, p. 17, pi. i. ff . 
f This anatomist regarded the “ calotte ” as wholly muscular, and its 
siphonal production as the tendon of such. Describing the retractores as 
“ ia game musculaire que traverse l’cesophage,” he proceeds, “ Son extre- 
mite anterieure qui va a la tete et aux appendices etait tronquee a 
1’endroit de l’arrachement; mais la posterieure etait bien conservee ; on 
voyait qu’allant en se rdtrdcissant elle s’attacliait a une lame charnue 
qui tapissait le fond de la premiere loge de la coquille, en formant une 
