14 
MARINE FAUNA OF ST. ANDREWS. 
stones which have been long untouched. It covers spaces 
several inches square; and its margin is generally rounded and 
“finished” like the border of a lichen. Most of the speci¬ 
mens have their surfaces elevated into firm rugse, resembling 
miniature mountain-ranges, some of the crests rising into 
flattened lobes f inch in height. There are at least two 
varieties of this sponge—the first of which, besides the equi¬ 
angular triradiate spicula of the skeleton, the minute acerate 
ones of the interstitial and dermal membranes, and the uni- 
curvo-cruciform, has many spined acuate spicula of consider¬ 
able dimensions and others of the same size approaching the 
fusiformi-spinulate character. In the other variety the latter 
kinds are so little developed, if present, as not to be dis¬ 
tinguished from the ordinary minute acerate forms. In both, 
almost all the latter are distinctly spined. 
Suborder II. Silicea. 
Hymeniacidon ficus , Esper; Bowerb. vol. ii. p. 206. 
Occasionally from deep water, attached to dead shells. Cla- 
vate specimens frequently grow from the smaller end of Den- 
talium entalis. This species seems to frequent muddy 
ground. 
Hymeniacidon celata, Grant; Bowerb. vol. ii. p. 212. 
Abundant in shells from deep water, between the layers of 
which it tunnels its devious tracks. This is one of the main 
agents in causing the disintegration of dead shells. 
Halicliondria panicea , Pallas ; Bowerb. vol. ii. p. 229. 
Scarcely a stone can be lifted near low-water mark, amongst 
the rocks, but has a patch of this common sponge. Under 
the cavernous ledges overhanging rock-pools it spreads its 
structure over the dark red Cynthia , matting together sea¬ 
weeds and corallines, and hanging in pendulous nodules on 
