104 PROCEEDINGS OF SOCIETIES. 



single Scottish example, though he had now found it very sparingly 

 in collections made from the south and west of Ireland. The 

 Scottish and Irish specimens are absolutely alike. 



nth August, 1876. 



Someiohat doubtful form of Stauroneis pliyllodes, exliibited. — 

 Eev. Eugene O'Meara showed a form of Stauroneis from Lough 

 Mask, which at first sight might be considered as undescribed, 

 but, on more careful investigation, he was disposed to regard it 

 as identical with that exhibited by him at the previous meeting, 

 diifering only in having the striae somewhat closer and finer. 



Exceptionally high-coloured brownish- crimson example ofHypnum 

 revolvens. — Mr. Pirn showed Hypniim revolvens from near the 

 base of Cam Tual Mouutain, Killarney, remarkable -as being 

 very richly coloured a deep brownish-crimson. 



Structure of spine of Phyllacanthus gigaiitea. — Mr. Mackintosh 

 exhibited a cross-section through the milled riug of the spine of 

 Phyllacanthus gigantea, A. Agass., and drew attention to its very 

 slight development. The typical structure (shown for comparison 

 Centrostephanus JRodgersii, A. Agass.) consists of a number of 

 separate segments with a somewhat petaloid arrangement of their 

 reticular tissue ; but in the specimen under notice this was en- 

 tirely absent, the peripheral part of the section being formed by 

 a network whose interspaces were less regularly arranged than 

 in the part nearer the centre. The feeble development of the 

 milled ring seems to be the rule amongst the Cidaridse. 



Mesentery of Echinus esculentus, Linn., exhibited. — Mr. Booker 

 exhibited a portion of the mesentery of Echinus esculentus. Linn., 

 which contained a number of minute rouuded cells (?) with 

 reddish-yellow pigment, and also numerous calcareous spicules 

 shaped like the letter C, with a nodular thickening in the middle 

 of the curve, somewhat like, but easily distinguishable from, those 

 figured by C. Stewart ('Trans. Liuii. Soc.,' vol. xxv), from the 

 ambulacral tube of Echinometra. 



New species ofOocystis, Nag. — Mr. Archer showed some recent 

 examples (none mounted could possibly present the same beauty) 

 of a unicellular algal form referable to Alex. Braun's genus Oocys- 

 tis, and, doubtless, forming a new species, at once distinguishable 

 by its large size, the broadly elliptic cells being in length 0'0024 to 

 ()-0027" in breadth 0-0020 to 0-0024," thus but shghtly longer 

 than broad. The cell-wall is, by comparison, very thick, with 

 the somewhat nodular little thickening at each pole (seeu also 

 in other species) ; the chlorophyll-granules, in examples in which 

 these were not too dense, could be seen arranged parietally in a 

 beautifully and curiously regularly reticulate manner, the 

 " meshes" or interspaces of the interior surface of the wall being 

 bare of them. Mr. Archer had seen only two young cells within 

 the expanded mother-cell, four, eight, to sixteen, being common 

 in Oocysfis Naegelii. In examples about to produce young indi- 

 viduals the contents become more dense and the reticulated 



