1-4 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 | 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-crucifonn, 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, 



Hymeniaddon 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 

 groimd. 



Hymeniaddon 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. 



Halichondria panicea, PaUas ; 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 

 structui-e over the dark red Cynthia, matting together sea- 

 weeds and corallines, and hanging in pendulous nodules on 



