Carter — Fossil Sponge- Spicules from Ben Bulben. . 191 



limestone belonging to the Carboniferous series which Mr. Thomson had 

 gathered from the western side of Black Head, county Clare, at the southern 

 extremity of the entrance to Galway Bay, in which the siliceous element (often 

 present in great quantity) seemed to indicate that it had been derived from 

 some organisms more or less composed of silica, especially as in other parts, 

 where the limestone is pure, the remains of sponge-spicules in a calcified state 

 are abundantly recognizable, although in none of the specimens sent to mo 

 could I find a definite form. 



Here the matter rested, so far as I myself was concerned ; but Mr. Joseph 

 Wright, F.G.S., who resides at Belfast, having subsequently visited the 

 mountain near Sligo called " Ben Bulben," actually ascertained the presence 

 of several forms of sponge-spicules in the limestone of the Carboniferous system 

 there, and kindly forwarded specimens of them to me, together with fragments 

 of the strata in which they are found, for description and illustration. But 

 before I proceed to this, it is desirable that the following extracts from Mr. 

 Wright's letter, dated Jan. 1, 1880, which accompanied them, should be given, 

 viz. : — 



"Last summer my friend Mr. S. A. Stewart spent a few days botanizing 

 on Ben Bulben, and, whilst there, observed soft clay bands in the limestone, 

 of which he brought me three different 'gatherings' to examine for Fora- 

 minifera, viz. : — 1, containing no organisms ; 2, a few Foraminifera and spi- 

 cules ; and 3, rich in sponge-spicules. 



" The last material proved so interesting that we afterwards visited the 

 place in company and brought away a quantity of the clay. It is of a pale 

 yellowish colour, and occurs interstratified with bands of chert, especially at 

 the summit of the mountain, where it is very soft, owing, apparently, to 

 exposure to the weather ; on the other hand, lower down, the same yellow 

 material occurs, but much harder, although lighter, from its open pumice-like 

 structure. At both places we found a great number of fossils belonging to the 

 limestone of the Carboniferous system, viz 



V I sent some of the clay to a friend in Cork for analysis ; and he has 

 informed me that it contains 98 per cent, of silica." 



After this follow sketches of all the forms of fossil sponge-spicules that 

 Mr. Wright by dexterous manipulation was enabled to extricate from the clay — 

 to which, after carefully looking over all that he found, which were subse- 

 quently forwarded to me, I can add no more specifically, although I have been 

 able to find a few with slightly different forms, which have assisted me in the 

 following descriptions. Of course, as drift-spicules, which these must have 

 been when originally deposited, to say nothing of the subsequent effects of 

 fossilization, &c, they are nearly all fragmentary ; but sufficient of them 

 remains for easy recognition and for restoration, as will be seen by the illus- 

 trations. 



First and foremost is a sexradiate stellate (PI. XIV. B. fig. 2), which in 



