18 Mr. W. .). Sollas on a new Genus and 
very numerous, frequently collected into longitudinal bundles 
(%• 5 ). 
Hab. Marine. 
Loc. (?). Collection, Bristol Museum. 
Obs. Two of the most important characters of this sponge 
are, first, the triradiate form of its echinating spicules, and, 
next, the extreme tendency to variation which these display. 
That the normal echinating spicule is truly triradiate, just 
as, say, a characteristic Iiexactinellid spicule is sexradiate, is 
proved by the triradiate form of its axial canal. In spicules 
Fig. 1. 
Diagrammatic section taken longitudinally through a papilla and one 
half of the stem of the sponge: a, «, axial line of the stem. 
which have not been subjected to any chemical treatment the 
canal is only just discoverable ; but by boiling them for three 
or four minutes in caustic alkali it becomes enlarged and is 
then very obvious. The cavity from which the three arms of 
the canal originate is frequently globular in shape, and ex¬ 
ceeds the canals in diameter ; it represents the position of the 
young spicule-cell before it had budded to produce the adult 
form ; and it may very conveniently be used as a fixed point 
within the spicule from which to measure the length of its 
diverging rays. 
To produce the normal form of echinating spicule, two buds 
must have sprouted from the inner or proximal face of the 
spicule-cell, and by growing obliquely into the sponge have 
