190 Carter — Fossil Sponge- Spicules from Ben Bulben. 



almost purely silicious. Mr. Cooke regards it as disintegrated chert, the 

 disintegrating agent being animal life. The following is Mr. Cooke's analysis : — 

 Silica, soluble and insoluble, 97 to 98 per cent. ; alumina, with sesquioxide of 

 iron, 1 per cent. ; lime, less than 1 per cent. ; traces of magnesia and man- 

 ganese, 1-10 per cent. Mr. Cooke finds clear proof of organic matter still 

 existing in the clay, and he considers that the silica was probably supplied by 

 some volcanic outburst. In the " rotten limestone " of Cunningham Baidland, 

 Ayrshire, which seems to resemble our Ben Bulben clay, sponge-spioules are 

 abundant, and very similar to those found in Sligo. In the Irish, as in the 

 Scotch beds, chert occurs associated with the clays in which the spicules are 

 found. This is similar to what occurs in our Cretaceous rocks, and points to 

 tbe fact of the silica which forms our flints and chert having been, in part at 

 least, derived from silicious sponges which abounded in ancient seas, the silica 

 being redeposited in layers, or concentrated round some sponge or other 

 organism, and so forming our nodular flints. The paper was illustrated by a 

 fine series of diagrams representing the various forms of spicules obtained in 

 the Sligo mountains, as well as the material in which they were found. 

 Several examples of recent and fossil sponges were also exhibited at the close 

 of the meeting. 



Through the kind permission of Mr. H. J. Carter, F.R.S., the following 

 paper, " On fossil sponge-spicules from the Carboniferous strata of Ben Bulben," 

 has been reprinted from the Annals and Magazine of Natural History, Sept., 

 1880 ; the figures which accompanied it have been reproduced by photo-lith- 

 ography, and are an exact reproduction of the originals. 



(From the Annals and Magazine of Natural HisTORr/or Sept., 1880.J 



ON FOSSIL SPONGE-SPICULES FROM THE CARBONI- 

 FEROUS STRATA OF BEN BULBEN, NEAR SLIGO. 



BY H. J. CARTER, F.R.S., &c. 



Plate VIIL, (lower half) Jigs. 1-17. 



WN the last contribution that Mr. James Thomson made to our knowledge of 

 W fossil sponges which existed during the Carboniferous epoch in the 

 ^ neighbourhood of Glasgow ('Annals,' 1879, vol. iii., p. 141, pi. xxi.), I 

 described and illustrated Holasterella conferta, a genus of sponges, as the 

 name indicates, exclusively composed of stelliform spicules, whose typical 

 figure, from the same locality, had been found and illustrated a year previously. 

 At the same time I added (ibid. p. 145) some observations on specimens of 



