212 Mr. H. J. Carter on Fossil Sjjonge-spicides. 



spines or flukes situated opposite each other, and still attached 

 to a small fragment of the shaft (fig. 9), longer and larger 

 portions of which may be observed in the " chert," both lon- 

 gitudinally and in transverse sections under fracture, indi- 

 cating that with the anchoring ends they are the fragmentary 

 remains of what originally were anchoring- or cord-spicules 

 of a Hyalonema or Sarcohexactinellid sponge. 



Tolerably numerous also are Lithistid spicules, especially 

 one like a tripod, in which the centre is convex and smooth, 

 while the three legs, bending outwards and downwards, end 

 respectively in expanded concave feet, which seem to show 

 that they were once applied to similar surfaces on adjoining 

 spicules (figs. 10 and 11). This in all probability was a 

 surface-spicule like those of Corallistes aculeata (' Annals,' 

 1880, vol. vi. pi. vii. fig. 45). Fragments of other Lithistid 

 spicules are also present, such as the dendritically branched 

 surface-spicule (fig. 12), and the shafted one of the fully 

 developed or internal structure (fig. 13). 



To these may be added a sausage-shaped spicule like that 

 of some of the Renierce of the present day, also tolerably 

 plentiful (fig. 14) ; and other fusiform acerate ones (figs. 15 

 and 16), which being common to many kinds of sponges, 

 cannot in their isolated state be identified with any in par- 

 ticular. 



Two fragments represent the arms of a quadriradiate spi- 

 cule (fig. 17) ; but whether these were equal in length, or one 

 was prolonged into a shaft, there is no evidence to show : if 

 the former, it probably belonged to one of the Pachastrel- 

 lina; if the latter, to a zone-spicule of one of the Pachy- 

 tragida. 



The most interesting part of this discovery, however, is 

 that the " clay " of Ben Bulben, in which Mr. Wright found 

 these remains, is apparently identical in every respect with 

 that sent me by Mr. James Thomson, in which he found 

 Holasterella conferta, near Glasgow. In both instances iso- 

 lated sponge-spicules of different kinds are disseminated 

 through it, which can be obtained by edulcoration with water, 

 and are composed of silica in an opaque or chalcedonic state, 

 rendered more or less irregular by the presence of rhomboidal 

 excavations on the surface. 



Here I might observe that, not only are the sponge-spicules^ 

 and the minute fossils of the Carboniferous Limestone which 

 accompany them, silicified and pitted on the surface with the 

 same kind of rhomboidal excavations, but the "chert" to 

 which Mr. Wright has alluded appears to be a solid pseudo- 

 morph of the limestone ; for its pumice-like worm-eaten cha- 



