ASTERACTINELLA. 173 
partially fused together, but this probably arises from the fossilization; the 
numerous instances in which the spicules are now entirely free seem to indicate 
that they were originally only held together by the soft structures of the Sponge. 
The character of these spicules clearly distinguishes them from the other 
detached forms with which they are associated ; and the occurrence of fragments 
of the Sponge-skeleton exclusively composed of them likewise shows that they are 
distinct. No trace of any derivation from the hexactinellid type is perceptible in 
any of these spicules; even in the simplest form more than six rays are present, 
and there is no indication that they may have originated from the subdivision of 
the rays of a normal hexactinellid spicule. 
Some of the spicules included in this genus were referred by Mr. Carter to 
Holasterella conferta, and relying on his definition I likewise relegated them to the 
same species in the ‘ Cat. Foss. Sponges ;’ but, as already mentioned, in a subsequent 
examination of the type form I have been unable to discover any of these forms 
in it. 
Two species of this genus have been recognised in the Carboniferous strata of 
Ayrshire. 
49. ASTERACTINELLA EXPANSA, Hinde, sp. nov. Plate VIII, figs. 3, 3 a—3 h. 
1877. Hyatonema Smiruir (in part), Young and Young. Ann. and Mag. Nat. 
Hist., ser. 4, vol. xx, pl. xiv, figs. 20, 21. 
1878. _— — ? (in part), Carter. Ann. and Mag Nat. Hist., ser. 5, 
vol. i, p. 133, pl. ix, fig. 11. 
1879. HoxastERELLA coNFERTA (in part), Carter. Ann. and Mag. Nat. Hist., 
ser. 5, vol. iii, p. 141, pl. 
xxi, figs. 4, 5, 7, cet. excl. 
1883. _— — Hinde. Cat. Foss. Sponges, p. 152, pl. xxxii, 
figs. 2—2 f. 
In the simpler spicules there is a prominent vertical ray, from the summit of 
which nine to twelve robust rays diverge at various angles; a variable number of 
small conical rays are also frequently present. In other spicules there is a distinct 
vertical axis, whilst not infrequently no distinct vertical ray or axis is present, and 
the spicule consists of seven to twelve rays of varying lengths in addition to 
several subordinate conical rays, all radiating from a common centre. The rays 
are straight or slightly curved, circular in transverse section, and they gradually 
taper to an obtuse point. The smaller central rays are sometimes divided at their 
tips. In a small spicule the principal rays are °65 mm. in length and -125 mm. 
Z 
