164) is here represented. Amongst the air-breathing
_Articulates_, we meet in the Oolitic rocks with the remains of
Spiders (_Arachnida_), Centipedes (_Myriapoda_), and numerous
true Insects (_Insecta_). In connection with the last-mentioned
of these groups, it is of interest to note the occurrence of
the oldest known fossil Butterfly--the _Paloeontina Oolitica_
of the Stonesfield slate--the relationships of which appear to
be with some of the living Butterflies of Tropical America.
[Illustration: Fig. 164.--_Eryon arctiformis_, a "Long-tailed
Decapod," from the Middle Oolites (Solenhofen Slate).]
Coming to the _Mollusca_, the _Polyzoans_, numerous and beautiful
as they are, must be at once dismissed; but the _Brachiopods_
deserve a moment's attention. The Jurassic Lamp-shells (fig.
165) do not fill by any means such a predominant place in the
marine fauna of the period, as in many Palaeozoic deposits, but
they are still individually numerous. The two ancient genera
_Leptoena_ (fig. 165, a) and _Spirifera_ (fig. 165, b), dating
the one from the Lower and the other from the Upper Silurian,
appear here for the last time upon the scene, but they have not
hitherto been recognised in deposits later than the Lias. The
great majority of the Jurassic _Brachiopods_, however, belong to
the genera _Terebratula_ (fig. 165, c, e, f) and _Rhynchonella_
(fig.
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