104 PROCEEDINGS OF SOCIETIES. 



that they continue to grow and increase in the fern-house at 

 Glasnevin, but have not yet produced female fruit. 



J^ew Aulacodisciis, shown . — Rev. E. O'Meara exhibited a species 

 of Aulacodiscus, the peculiarities of which he thought had 

 hitherto escaped the notice of observers. The form bad frequently 

 come under his notice when examining the Richmond and Mary- 

 land deposits, and in other localities, where he found it difficult to 

 assign it to its projjer genus. A very careful examination with 

 good illumination, however, recently brought out its latent 

 characters and enabled him to give it its place in the genus 

 Aulacodiscus. When examined in a dry state the form is so dark 

 that its features are quite indistinguishable, and even when 

 mounted in balsam it requires very exact adjustment to bring 

 them out. An areolate surface is ever observable, the areoles 

 being large and distinctly hexagonal, but over the areoles there 

 is superimposed a surface marked with distinctly radiate puncta, 

 and only when this surface is exactly in focus, do the marked 

 features of the genus Aulacodiscus reveal themselves. The 

 nodules are usually six in number, very small, and sub-marginal. 

 The furrows connecting them with the centre are narrow and 

 difficult to discern. Considering the size, the general aspect of 

 this form, as well as the locality, Mr. O'Meara considered it 

 likely that this is the form figured by Ehrenberg as Coscinodlsciis 

 aster omplialus, ' Microgeologie,' t. xviii, f. 45 a, b. The central 

 rosette of elongated areoles, so conspicuous in the figure, is in 

 this case absent, but there is an indistinct appearance of it when 

 viewed with a low power. He proposed to name the form Aula- 

 codiscus areolatus. 



Exliihition of " Moss-copper'" — Mr. Crowe showed examples 

 of metallic copper, in the form known as " moss-copper," forming 

 an exceedingly pretty low-power object. This was from a new 

 locality, Glendalough Mines, Co. Wicklow, 



Structure of Spines of Diadema mexicanmn. — Mr. Mackintosh 

 exhibited sections of the spines of Diadema mexicanum, kindly 

 given him by Dr. Giinther, E.R.S., British IMuseum, which pre- 

 sented the peculiarity of having dimorphic spines — a condition 

 which, though characteristic of a closely allied genus Centro- 

 stephanus, Peters, he had not met with previously in Diadema. 

 The majority of the spines were of the usual shape, long, 

 cylindrical, and closely verticillate, and, in section presented no 

 difference of any importance from the typical structure described 

 in ' Transactions of the Royal Irish Academy,' vol. xxv, plate 16, 

 1875. On the actinal (oral) aspect of the corona were a few 

 spines, which externally diflered only in size and colour from the 

 fusiform spines of Centrostephanus (loc. cit.), in section also 

 presented a striking resemblance to them, whilst sparsely scat- 

 tered over the corona were to be seen spines which were exactly 

 intermediate in form and structure between the two. 



Ahnormal example of Eu(/lypha. — Mr. Archer showed an ab- 

 normal example of tiie test of the Euglyplui he had named 



