differs in the greater length of the articulations of the stem, 
rather a variable character ; and m 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. xigrescens, 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 spe- 
cimens, 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. PotystpHoNtIA aFrinis:—the natural size. 2.Small branch, with 
capsules. 3. Portion of the same. 4. A ramulus with imbedded tetra- 
spores. 5. Articulations of the stem. 5. Transverse section of the stem : 
—all magnified. 
