HYALOSTELIA. 109 
Growp.—LyYSssaKINA. 
Family.—PouaKinm. 
Genus.—HyatostELia, Zittel ; Emend. Hinde. 
1878. Handbuch der Palzontologie, Bd. i, Lief. 2, p. 185. 
Syn.—Pyritonema, M‘Coy ; Acestra, I’, Roemer ; Acanthospongia, Young (non 
M‘Coy) ; Hyalonema, Young, Carter (in part) ; Serpula, Portlock, M‘Coy (in part) ; 
Astroconia P Sollas. 
Generic Characters.—Complete form of Sponge unknown ; the body-portion is 
composed partly of simple hexactinellid spicules in which one axis is usually much 
elongated, and partly of spicules in which one or more of the rays are inflated, 
spined, reduced to rounded knobs, or even absent. The dermal layer is mainly 
formed of large spicules in which the distal ray is reduced to a blunted process. 
The anchoring appendage consists of elongated, cylindrical, rod-like spicules, 
which are either separate, or in rope-like bundles, and sometimes terminate in four 
recurved rays. 
This genus was based by Prof. Zittel on the characters of Hyalonema Smithii, 
as described by Messrs. Young and Young.’ These authors, however, included in 
the type-species a great variety of forms of detached spicules, some of which 
belong to distinct genera. Thus, for example, the spicules with from six to eight 
horizontal rays, mentioned in Zittel’s diagnosis of the genus, do not belong to the 
same Sponge as the simple hexactinellid spicules. This has been proved by the 
subsequent discovery of fragments of spicular mesh, in some of which hexactinellid 
spicules and their modifications are exclusively present, whilst others are composed 
only of the umbreila-shaped spicules with numerous horizontal rays.” I have 
therefore proposed that the skeletal-spicules in Hyalostelia Smithii, which has 
been taken as the type of the genus, should be restricted to such simple and 
modified hexactinellids as are present in the connected fragments of skeleton, and 
that the umbrella- and stellate-spicules should be excluded from it. The body- 
spicules do not appear to have been originally attached together in any way ; 
those occurring in the fragments of the skeleton which have been met with are 
held together by a secondary deposit of silica. 
The elongated anchoring spicules of the Sponge are present in great abundance 
in the same beds with the body-spicules, and are therefore assumed to have 
1 «Ann. and Mag. Nat. Hist.,’ ser. 4, vol. xx, p. 425, pls. xiv, xv. 
2 «Cat. Foss. Sponges,’ p. 150. 
