146 BRITISH PALASOZOIC SPONGES. 
(‘ Phil. Trans.,’ 1885, Pl. xh, 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.—Haruistion, Young and Young. Hmend. Hinde. 
1877. Annals and Mag. Nat. Hist., ser. 4, vol. xx, p. 428. 
Syn.—Rhaphidhistia, Carter ; Dysidea (in part), Carter. 
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 (Pl. 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. 
