HYALOSTELIA. 161 



41. Hyalostblia paeallela, M'Ooy sp. Plate VI, figs. 3, 3 a — 3 g. 



1844. Sebptjla paeallela, M'Coy. Synop. Carb. Foss. Ireland, p. 169, pi. xxiii, 



fig. 30. 

 1843. — socialis, Portlock (non Goldfuss). Geol. Keport Londonderry, 



p. 362, pi. xxv A, figs. 

 9 a, 9 b. 

 1854. — paeallela, Morris. Cat. Brit. Foss., p. 92. 

 1866. Hyalonema paealleltjh, Suess. Ann. and Mag. Nat. Hist., ser. 3, vol. 



xviii, p. 404. 

 1878. — Toungi ?, B. Etheridge,jun. Geol. Mag., vol. v, p. 119. 



1880. Acestea paeallela, F. Boemer. Lethaea Pal., p. 318, fig. 60. 



1880. Saecohexactinellid, Carter. Ann. and Mag. Nat. Hist., ser. 5, vol. vi, 



p. 211, pi. xivB, figs. 8, 9. 



1881. Acestea paeallela, Nathorst. Om spar af nagra evertebrade djur., Kong. 



Svenska. vetensk. Akad. Handl., Bd. 18, 

 No. 7, p. 46. 

 1883. Htalostelta — Hinde. Cat. Foss. Sponges, p. 151. 



This species includes simple and modified hexactinellid spicules, probably 

 belonging to the body-skeleton and the dermal layer, together with fragments of 

 the spicular bundles, and detached rod-like spicules, forming the anchoring appen- 

 dages of the Sponge. In the spicules of the dermal layer only five rays are present, 

 the distal ray not being developed. The transverse rays are straight or slightly 

 curved, nearly cylindrical, or but slightly tapering, and terminate obtusely. The 

 rays vary from - 45 to 1*5 mm. in length, and from 1 to '25 in thickness. The 

 spicules are siliceous, and in some specimens the canals are preserved. 



The elongated spicular rods of the anchoring-rope of the Sponge have smooth, 

 even surfaces, and appear to be cylindrical. Near the distal ends they slightly 

 expand, and they terminate in conical extremities with four short, stout, recurved 

 points or rays. The canals in these spicular rods are usually preserved, and in 

 some instances the concentric layers can be seen (PL VI, fig. 3/). As a rule they 

 are now of chalcedonic silica, but in some cases the silica has been replaced by 

 calcite. The anchoring-spicules sometimes occur detached from each other, and 

 widely spread out on the surface of the rock ; not unfrequently they are grouped 

 into compressed bundles of 5 to 9 mm. in width, in which the component spicules 

 are nearly in contact and disposed parallel to each other. Fragments of these 

 bundles or ropes occur, having a length of 140 mm. The individual rods in the 

 same bundle exhibit considerable variation in size ; they range from "05 to "5 mm. 

 in thickness. 



This species was originally proposed by Portlock for narrow bands or bundles of 



