FAMILY 2. SIPHONOIDEA. 303 
his boat above him, and with his head and barbs upon the ground, 
making* a tolerably quick progress. He keeps himself chiefly upon the 
ground, creeping sometimes also into the nets of the fisherman; but 
after a storm, as the weather becomes calm, they are seen in troops 
floating on the water, being driven up by the agitation of the waves: 
whence one may infer that they congregate in troops at the bottom. 
This sailing, however, is not of long continuance; for having taken in 
all their tentacles, they upset their boat, and so return to the bottom.” 
This account, published at Amsterdam more than a hundred years ago, 
is mainly authenticated ; but it may still be a little exaggerated, for the 
Nautili have never since been found floating in troops, nor exercising the 
bold familiarity, above-mentioned, of walking into the fisherman’s nets. 
The shell of Nautilus may be described as being orbicular, symmetri- 
cal, divided into a number of chambers, generally about forty, and con- 
voluted on a vertical plane, with the whorls contiguous, the last one 
completely covering all the others. It is a firm shell, distinctly marked 
with transverse brownish bands, and is composed of two distinct layers, 
an outer coat of opake testaceous substance, and a lining of bright nacre. 
The axis of the spire is umbilicated on each side, and the umbilicus is 
sometimes open, sometimes filled up with the matter deposited by the 
overlapping fold of the anterior portion of the mantle. The septa which 
divide the chambers are convex on the inside, and perforated throughout 
with a central siphonic tube, which is more or less calcareous ; the aper- 
ture of the shell is large, and the margins are simple. The muscular 
impression of the horny girdle by which the animal has been attached to 
its shell may be distinctly observed in every chambert. 
* By force of gravity probably. 
+ We have somewhat exceeded the usual limit of our observations in speaking of the Nau- 
tilus, but the fulness and importance of its history demand especial service. It is important 
to the naturalist, but far more so to the geologist ; for, as Professor Owen eloquently expresses 
it, “it is the living, and perhaps sole living archetype of a vast tribe of organized beings, 
whose fossilized remains testify their existence at a remote period, and in another order of 
things.” 
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