differs in the greater length of the articulations of the stem,
rather a variable character; and in the smaller number of siphons
in each whorl. The ramification is somewhat more lax; the
spaces of naked branch at the bases of the branching portion are
longer; the filaments are more flexuous and flaccid, and the
colour is usually paler than in P. nigrescens, but there is such a
general similarity that I could be well contented to regard it as
a deep-water form of that species. I have endeavoured, in the
accompanying plate drawn from one of Mr. Moore’s original specimens,
to show all the characters proper to the species. P. affinis
was first observed, some twenty years ago, on the coast of Antrim
by Dr. Drummond of Belfast, and was soon afterwards found, in
considerable plenty on the same coast, at a station a few miles
distant by Mr. Moore, and was by the latter gentleman described
and figured in the Survey Report of Londonderry. In the
present year (1850) I collected a few specimens in Mr. Moore’s
locality.
Fig. 1 . P oL Y S iPH O N T A A F F IN I S :— the natural size. 3. Small branch, with
capsules. 3. Portion of the same. 4. A ramulus with imbedded tetraspores.
5. Ai-ticulations of the stem. 5. Transverse section of the stem :
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