Amongst the more important of these may be mentioned
_Crioceras, Turrilites, Scaphites, Hamites, Ptychoceras_, and
_Baulites_. In the genus _Crioceras_ (fig. 204, d), the shell
consists of an open spiral, the volutions of which are not in
contact, thus resembling a partially-unrolled _Ammonite_ or the
inner portion of an _Ancyloceras_. In _Turrilites_ (fig. 203), the
shell is precisely like that of the _Ammonite_ in its structure;
but instead of forming a flat spiral, it is coiled into an elevated
turreted shell, the whorls of which are in contact with one another.
In the genus _Scaphites_ (fig. 204, e), the shell resembles that
of _Ancyloceras_ in consisting of a series of volutions coiled
into a flat spiral, the last being detached from the others,
produced, and ultimately bent back in the form of a crosier; but
the whorls of the enrolled part of the shell are in contact,
instead of being separate as in the latter. In the genus _Hamites_
(fig. 204, f), the shell is an extremely elongated cone, which
is bent upon itself more than once, in a hook-like manner, all
the volutions being separate. The genus _Ptychoteras_ (fig. 204,
a) is very like _Hamites_, except that the shell is only bent
once; and the two portions thus bent are in contact with one
another. Lastly, in the genus _Baculites_ (fig. 204, b and
c) the shell is simply a straight elongated cone, not bent
in any way, but possessing the folded septa which characterise
the whole Ammonite family.
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