168 BRITISH PALAOZOIC SPONGES. 
rays, at a short distance from the central axis, divides into three secondary pointed 
tapering rays. The diameter of this form is ‘4 mm., and the thickness of the rays 
near the centre is 04mm. These spicules are very unfavorably preserved; they 
are not uncommon in a boulder of chert fromthe Drift at York, associated with 
spicules of Reniera and other forms like those in the chert-beds at Richmond; it is, 
therefore, probable that it may originally have been derived from this neighbour- 
hood. A flesh-spicule of a nearly similar form, but of very much smaller proportions, 
has been figured by Dr. Bowerbank from Huplectella aspergillum, Owen.' 
Sub-Order.—HEtuRActINELLID®. 
Genus.—THOLIASTERELLA, Hinde, gen. nov. 
Syn.—Holasterella (in part), Hinde ; ? Hyalonema (in part), Carter. 
Form of Sponge unknown; the skeleton consists of spicules, which, as suggested 
by Mr. Carter, bear a general resemblance to the handle and ribs of an umbrella. 
The handle or vertical ray of the spicule supports on its summit a variable number 
of rays which radiate from it in a generally horizontal direction. A central disc of 
variable proportions is formed by the union of the bases of the horizontal rays and 
the upper surface of this, and of the rays, may be either smooth or covered with 
tubercles or blunted vertical spines. In some cases spicules of an irregular form 
are present, in addition to the normal umbrella-spicules. 
The spicules of the body of the Sponge appear to have been aggregated 
together without definite arrangement; they seem to have been mostly free from 
each other, and merely held in position by the interlacing of their rays; but in 
some cases the rays appear to have been partially cemented together. The outer 
surface or dermal layer of the Sponge consisted of a framework with irregular 
interspaces, formed by the intervening and partial fusion of the horizontal rays of 
larger and smaller “‘ umbrella” spicules, whilst the shafts of these spicules pene- 
trated into the interior of the Sponge. 
The spicules on which this genus is based were recognised both by Messrs. 
J. and J. Young and by Mr. Carter, and in the ‘ Cat. Foss. Sponges’ I described 
them as a species of Holasterella. 
Since then Mr. James Bennie, Mr. John Smith, and also Mr. John Young, 
have supplied me not only with many fresh examples of detached spicules, but 
with fragments of the skeletal-structure in which the spicules are in their original 
1 «Mon. of the Brit. Spongiade,’ vol. i, p. 258, pl. viii, fig. 189. 
2 @oNa, a hat to keep the sun off, a parasol ; aorjp, a star, dimin. 
