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INHABITING MULTILOCULAR SHELLS. 283 
whole, however, since the shell of the Scaphite is compact and 
strong, and the siphuncle often of moderate size, it may have be- 
longed to an animal with some power of locomotion ; and this seems 
the more prebable from its occurring in a fossil state most commonly 
in the green sand formation, and not when the bottom of the sea 
could have had much mud for animals to burrow in. 
The Ammonites, of which we have already said so much, need 
not now detain us long. The Goniatites have the siphuncle nearly 
always so extremely small that one cannot, with any degree of pro- 
bability, suppose it to have served any very useful purpose. Of the 
other groups, some have also a mere thread, instead of an extensible 
tube ; while in others the organ is larger, and doubtless was of more 
importance to the animal: but the number of these latter is not, I 
think, great in proportion to the whole, and, for the most part, it 
seems probable that Ammonites were not endued with great power 
of locomotion. 
The Hamites, perhaps, with Spirula, and other genera of which 
the whorls are not contiguous, must be ranked among internal 
shells. If so, the animal, in all probability, swam freely in the wa- 
ter; and from the comparative abundance of the fossils of this ge- 
nus, some of them extremely large, the former owners doubtless 
worked great havoc on the population of the ancient seas of the pe- 
riod at which they lived. It may be observed here, by the way, 
that, although the species of this genus are not very nnmerous, the 
individuals of these few species seem to have been unusually plenti- 
ful; and although perfect specimens are rare, there is hardly a 
more common fossil in the greensand than the broken pieces of 
Hamites, some of them measuring as much as four or five inches in 
the diameter of the chamber. 
Coming now to the Baculites, we have a shell at ieast as fragile 
as the Turrilites, and of a shape still more exposed to injury from 
the slightest touch. The siphuncle, too, is extremely minute ; and 
nothing can be conceived more delicate than the whole appearence 
of the fossil. There are, however, specimens in the most beautiful 
state of preservation, and far more complete than any that exist of 
Turrilites. Probably the shells of this genus, as well as of Ha- 
mites, were internal ; but it would seem not unlikely, both from their 
remains occurring only in the chalk, and also from the unimportance 
of the siphuncle, that the shell merely formed a light skeleton, co- 
vered by the mantle of the animal, and that the necessary prey was 
obtained chiefly from the crustacea and shell-fish in the calcareous 
mud, 
