lls, or the Cephalopods, represented chiefly in the
earlier periods by the straight Orthoceratites described in a previous
article, are now curled in a close coil, and the internal structure
of their chambers has become more complicated. The subjoined wood-cut
represents a characteristic Chambered Shell of the Carboniferous age.
Goniatites is the scientific name of these later forms. If we had looked
for them in the Devonian period, we should have found many with looser
coils than these, and some only slightly curved in the shape of a horn.
These, as well as the perfectly straight forms, still exist in the coal
period, but the Goniatites with close whorls are the more numerous and
more characteristic.

[Illustration]

The Articulates have gained their missing class since the close of the
Devonian period, for Insects have come in, and that division of the
Animal Kingdom is therefore complete, and represented by three classes,
as it is at present. Of the Worms little can be said; their traces are
found as before, but they are very imperfectly preserved. There are
still Trilobites, but they are very few in number, and other groups of
Crustacea have been added.

One of the most prominent of these new types bears a striking
resemblance to the Horse-Shoe Crab of present times.

[Illustration]

[Illustration]

I here present one of our common Horse-Shoe Crabs above one of these
old-world Crustaceans, and it will be seen, that, while the latter
preserves some of the Trilobitic characters, such as the marked
articulations on the posterior part of the body and their division into
three lobes, yet in the prominence of its anterior shield, its more
elongated form, and tapering extremity, it resembles its modern
representative. In some of them, however, there is no such sharp point
as is here figured, and the body terminates bluntly. There were a large
number of these Entomostraca in the Carboniferous period, a group which
is chiefly represented among living Crustacea by an exceedingly minute
kind of Shrimp; but in those days they were of the size of our Crabs and
Lobsters, or even larger, and the Horse-Shoe Crab still maintains their
claim to a place among the larger and more conspicuous members of the
class.

The Insects were few, and, as I have said above, of a kind which seeks a
moist atmosphere, or whose larvae live altogether in water. They are not
usually well preserved, as will be seen from the broken character of