112 BRITISH PALEOZOIC 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 Gorgonidse. 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 Eophyton ? ewplanatum ; 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 strise are not developed in any of the spicules of this 

 latter form. 



Distribution. — Cambrian : Tremadoc 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. — Lithistid^:. 



Family. — Anomocladina. 



Genus. — Astylospongia, F. Boemer. 



I860. 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 



