i 9 4 Carter— Fossil Sponge-Spicules from Ben Bulben. 
composed of them), rendered still more fragmentary by partial removal so as 
to leave nothing but their moulds, as before stated, are those which at last 
come out entire, so far as they go, in the washing of the “ clay.” 
It is remarkable, too, that by far the most plentiful among Mr. Thomson s 
collection of spicules from the clay near Glasgow is that of Holasterella conferta i, 
as it is that of H. Wrightii at Ben Bulben; the “sausage-shaped” spicule 
(•fig 14) is also analogous to that of the supposed Remend sponge ( Annals, 
1879, vol. iii.pl. xxi. fig. 11), and about the same in frequency. In Mr 
Thomson’s collection were also fragments of Lithistid spicules; and last 
summer he sent me a section of an entire sponge in Carboniferous Limestone, all 
calcified withweathered-ont spicules on the surface, but none of it sufficiently 
defined for useful delineation. The collection also contained some zone-spicules 
of the Pachytragida ; so that, altogether, the Spongida appear to have been as 
plentiful and as varied in the Carboniferous age as at any other time. 
It would be worth while, when the opportunity offers, for some one to look 
over the weathered surface of the strata in the mountain of Ben Bulben, where 
fragments, if not entire specimens, of sponges from which the spicules come 
might be found, after the manner that they have been discovered in the Car- 
boniferous system in the south-west of , Scotland. 
11 
u fjttl * JT ^ 
