One of these interesting primitive insects, namely,
_Platephemera antiqua_ (fig. 89), appears to have measured five
inches in expanse of wing; and another (_Xelloneura antiquorum_) has
attached to its wing the remains of a "stridulating-organ" similar
to that possessed by the modern Grasshoppers--the instrument, as
Principal Dawson remarks, of "the first music of living things
that Geology as yet reveals to us."
[Illustration: Fig. 89.--Wing of _Platephemera antiqua_ Devonian,
America. (After Dawson.)]
Amongst the _Mollusca_, the Devonian rocks have yielded a great
number of the remains of Sea-mosses (_Polyzoa_). Some of these
belong to the ancient type _Ptilodictya_, which seems to disappear
here, or to the allied _Clathropora_ (fig. 90), with its fenestrated
and reticulated fronds. We meet also with the graceful and delicate
stems of _Ceriopora_ (fig. 91).
[Illustration: Fig. 90.--Fragment of _Clathropora intertexta_,
of the natural size and enlarged. Devonian, Canada. (Original.)]
[Illustration: Fig. 91.--Fragment of _Ceriopora Hamiltonensis_,
of the natural size and enlarged. Devonian, Canada. (Original.)]
[Illustration: Fig. 92.--Fragment of _Fenestella magnifica_, of
the natural size and enlarged. Devonian, Canada. (Original.)]
[Illustration: Fig. 93.--Fragment of _Retepora Phillipsi_, of
the natural size and enlarged.
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