Nevertheless, seeing that there is nothing in nature at all like
the chambered shell of the Belemnite, except the shells of the
Nautilus and of the
Spirula, it was legitimate to
prophesy that the animal from which the fossil proceeded must
have belonged to the group of the
Cephalopoda.Nautilus and
Spirula are both very rare animals,
but the progress of investigation brought to light the singular
fact, that, though each has the characteristic cephalopodous
organisation, it is very different from the other. The shell of
Nautilus is external, that of
Spirula internal;
Nautilus has four gills,
Spirula two;
Nautilus has multitudinous tentacles,
Spirula has
only ten arms beset with horny-rimmed suckers;
Spirula,like the squids and cuttle-fishes, which it closely resembles,
has a bag of ink which it squirts out to cover its retreat when
alarmed;
Nautilus has none.
No amount of physiological reasoning could enable any one to say
whether the animal which fabricated the Belemnite was more like
Nautilus, or more like
Spirula. But the accidental
discovery of Belemnites in due connection with black elongated
masses which were: certainly fossilised ink-bags, inasmuch as
the ink could be ground up and used for painting as well as if
it were recent sepia, settled the question; and it became
perfectly safe to prophesy that the creature which fabricated
the Belemnite was a two-gilled cephalopod with suckers on its
arms, and with all the other essential features of our living
squids, cuttle-fishes, and
Spirulae.
Pages:
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33