146 BRITISH PALEOZOIC SPONGES. 



(' Phil. Trans.,' 1885, PL xli, figs. 8 a — d), but it has a distinctly inflated summit : 

 it is a much smaller form than the spicules placed under A. vetusta. 

 Distribution. — Carboniferous Limestone : Clitheroe, Lancashire. 



Genus. — Haplistion, Young and Young. Emend. Hinde. 

 1877. Annals and Mag. Nat. Hist., ser. 4, vol. xx, p. 428. 



Syn. — Rhaphidhistia, Carter; Dysidea (in part), Garter. 



Generic Characters. — Sponges small, ovoid, spheroidal, or discoidal in form, 

 destitute of stem. Skeleton consisting of solid, reticulate, anastomosing fibres, 

 which terminate at the surface in small blunt projections. No special dermal 

 layer preserved. No definite canals beyond the irregular open spaces between the 

 fibres. The fibres are composed of minute, straight, or curved acerate spicules, 

 disposed generally parallel with the direction of the fibre, and interlacing with 

 each other. 



The authors of the genus state, in their original description, that " no spicules 

 have been recognised as belonging to the fossil, though the teazed-out tissue 

 lining the canals has a tantalising suggestion of spicules about it. It is not, there- 

 fore, absolutely certain that we have to do with a siliceous Sponge ; it may be that 

 a horny Sponge like Dysidea has become siliceous, as have the Brachiopod shells 

 in the same deposit." Through the kindness of Dr. J. R. S. Hunter, of Carluke, I 

 have been enabled to examine the example of Haplistion Armstrongi, described and 

 figured by Messrs. Young as the type of the genus, and the same specimen has 

 been here refigured (PI. V, fig. 1). It shows very distinctly the minute spicules 

 weathered out on the exterior of the fibres, and there can be no doubt that the 

 type of the genus is a siliceous monactinellid Sponge. The oscula referred to by 

 Messrs. Young are merely the irregular apertures between the reticulating fibres, 

 and the canals are of the same character. 



The genus Rhaphidhistia, Carter, is based on specimens having all the characters 

 of the present genus, which has the priority of publication ; and further, the same 

 author has referred to a new species of Dysidea specimens which clearly belong to 

 the typical forms of Haplistion. 



The examples of this genus are of rare occurrence, and they are at present 

 only known from the Carboniferous series of Ayrshire. 



