Amongst other well-known Devonian Brachiopods may be mentioned
the two long-lived and persistent types _Atrypa reticularis_
(fig. 97) and _Strophomena rhomboidalis_ (fig. 98). The former
of these commences in the Upper Silurian, but is more abundantly
developed in the Devonian, having a geographical range that is
nothing less than world-wide; whilst the latter commences in the
Lower Silurian, and, with an almost equally cosmopolitan range,
survives into the Carboniferous period.
[Footnote 17: The name of this genus is often written _Productus_,
just as _Spirifera_ is often given in the masculine gender as
_Spirifer_ (the name originally given to it). The masculine
termination to these names is, however, grammatically incorrect,
as the feminine noun _cochlea_ (shell) is in these cases
_understood_.]
[Illustration: Fig. 98.--_Strophomena rhomboidalis_. Lower Silurian,
Upper Silurian, and Devonian of Europe and America.]
[Illustration: Fig. 99.--Different views of _Platyceras dumosum_,
of the natural size. Devonian, Canada. (Original.)]
The Bivalves (_Lamellibranchiata_) of the Devonian call for no
special comment, the genera _Pterinea_ and _Megalodon_ being,
perhaps, the most noticeable. The Univalves (_Gasteropods_), also,
need not be discussed in detail, though many interesting forms
of this group are known.
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