158 BRITISH PALAEOZOIC SPONGES. 



Sub-Order. — HEXACTiNELLiDiE. 



Group. — Lyssakina. 

 Genus. — Htalostelia, Zittel. 



40. Htalostelia Smithii, Young and Young sp. Plate VI, figs. 1, 1 a — 1 I, 2, 2 a 



—2 k. 



1876. Acanthospongia Smithii, Young and Young. Cat. Western-Scottish 



Fossils, p. 38. 



1876. Hyalonema paeallelttm, Young (non M'Coy). Ibid., p. 38. 



1877. Acanthospongia Smithii, Carter. Ann. and Mag. Nat. Hist., ser. 4, 



vol. xx, p. 176. 

 1877. Hyalonema — (in part), Young and Young. Ann. and Mag. 



Nat. Hist., vol. xx, p. 426, pi. xiv, 

 figs. 1—3, 5—12, 14—17 ; pi. xv, 

 fig. 30. 



1877. Acanthospongia — Zittel. Studien, Abth. 1, p. 60. 



1878. Hyalonema parallela, R. Etheridgejun. Geol. Mag., new ser., vol. v, 



p. 119. 

 1878. — Smithii (in part), Carter. Ann. and Mag. Nat. Hist., ser. 5, 



vol. i, p. 129, pi. ix, figs. 1—9, 

 12, 13. 



1878. Htalostelia — Zittel. Handbuch der Pal., vol. i, p. 185. 



1879. Hyalonema — Nicholson. Man. of Pal., vol. i, p. 145. 



1880. — ? Girvanense, Nich. and Ether., jun. Mon. Silur. Foss. 



Girvan, Fas. ii, p. 239, pi. xix, figs. 1 — 1 b. 

 1880. Acanthospongia Smithii, F. Roemer. Lethsea Pal., p. 317. 

 1883. Hyalostelia — Einde. Cat. Foss. Sponges, p. 150, pi. xxxii, 



figs. 1, 1 a — \g. 



Entire form of Sponge unknown ; the portions preserved are fragments of the 

 dermal layer with the spicules in situ, detached skeletal-spicules of various forms 

 and dimensions, and bundles of elongated, rod-like spicules, and isolated fragments, 

 forming the anchoring appendage of the Sponge. 



The dermal layer of the Sponge consists of relatively large hexactinellid 

 spicules in which the distal ray of the vertical axis is reduced to a small rounded 

 knob or process, or is altogether wanting, whilst the transverse rays are of unusual 

 length, and incline downwards from the central node (PI. VI, fig. 1 a). These 

 spicules are disposed so that their transverse rays overlap each other, and thus form 

 quadrate interspaces which are partially filled by smaller spicules, whilst the 



