112 BRITISH PALASOZOIC SPONGES. 
thickness, in others they reach to ‘7 mm. In every instance smaller spicules are 
intermingled in the same bundles with the larger. In all the specimens examined 
the spicules are composed of chalcedonic silica. 
The larger bundles, which are not infrequent in the Llandeilo strata of Pont 
Ladies, are usually curved and folded over in various ways, which appear to result 
from the compressing and folding of the rocks in which they are enclosed. 
M‘Coy correctly compared this species with the anchoring rope of the recent 
Hyalonema, which at that time was regarded as a zoophyte, and it is placed in 
Morris’s catalogue with the Gorgonidee. The specimen discovered by Dr. Hicks 
in the Tremadoc strata of St. David’s, was originally described by him as 
a vascular cryptogam under the name of Hophyton ? eeplanatum ; its true nature 
appears to have been first noticed by Dr. Nathorst, who pointed out its similarity 
to M‘Coy’s species. 
In the size of the spicules forming the bundles the present species corresponds 
very closely with Hyalostelia parallela, M‘Coy sp., from the Carboniferous strata 
of Ireland, but transverse striz are not developed in any of the spicules of this 
latter form. 
Distribution.—Cambrian : Tremadoce strata, St. David’s (Dr. Hicks). Ordo- 
vician: Llandeilo, Tre Gil, south of Llandeilo (M‘Coy) ; Meadowtown, Pont Ladies, 
Mincop, Shelve, Shropshire (Mr. G. H. Morton); near Builth ? (Wyatt-Edgell 
Coll. in Geol. Surv. Museum) ; Dobb’s Linn, Moffat (Prof. Dr. H. A. Nicholson). 
ORDOVICIAN SPONGES. 
Sub-Order.—LitHistipm. 
Family.—ANoMocuaDINA. 
Genus.—AstyYLosponaciA, FH’. Roemer. 
1860. Die silurische Fauna des westlichen Tennessee, p. 5. 
Syn.—Siphonia, in part Goldfuss ; Hisinger. 
Generic Characters.—Sponges sub-spherical or ovate in form, simple, free, with 
rounded bases, in which there is no indication of any surface of attachment. Two 
systems of canals are present, one extending from the outer surface towards the 
centre of the Sponge, and the other of large canals which have a generally vertical 
direction, following the outlines of the Sponge, and opening either into a shallow 
