AJfD PHYSIOLOGY OP THE SPONGIAD^. 
1133 
Hah. Rocks between high and low water mark. Torquay. Gouliot Caves, Sark. Coast 
of Ireland ( J. S. Bowerbank). Orkney Islands, thirty-five fathoms (Captain F. W. L. 
Thomas, R.N.). Wick, Scotland (C. W. Peach). 
Exaniined in the hve state. 
Tethea cranium, Lamarck. 
Tethea cranium, Johnston. 
Sponge ovoid or subspherical, sessile surface even, strongly hispid. Dermal coat thick, 
abundantly furnished with short, stout, fusiformi-acerate spicula surrounding the 
large defensive fasciculi at various angles to their axes ; also profusely furnished 
with minute sigmoid bihamate spicula, dispersed irregularly. Dermal membrane 
thin, pellucid. Oscula and pores inconspicuous. Spicula of the skeleton fusiformi- 
acerate, large and long. Defensive spicula external, collected in fasciculi; fusi- 
formi-acerate, large and long, fusiformi-porrecto-temate, and a few fusiformi- 
recurvo-temate very long and slender. Sarcode abundantly furnished with minute 
sigmoid bihamate spicula. Gemmules lenticular, surface smooth, very tough and 
strong ; of two distinct sorts : the first furnished abundantly with slender fusi- 
formi-acerate spicula radiating in fasciculi from the centre to near the surface of 
the gemmule ; the second furnished abundantly with slender fusiformi-acerate, 
slender unihamate attenuated, and with short slender porrecto-temate spicula, 
mixed in fasciculi which cross each other irregularly. 
Colour pallid green. 
Hah. Island of Fulah (Jameson). Haaf Banks, Shetland (Barlee and Bowerbank). 
Examined in the fresh state. 
In the specimens of specific descriptions which I have given above, there are fortu- 
nately numerous characteristic points by which we may readily separate them from their 
congeners ; but this abundance of characters does not always exist. Thus in Halichondria 
caduca we find the structures so few and simple, as to render their description exceed- 
ingly difficult and unsatisfactory. 
Halichondria caduca, Bowerbank. 
Sponge massive, sessile, surface rugged. Oscula simple, small, dispersed, numerous. 
Pores inconspicuous. Dermal membrane aspiculous, pellucid, thin. Spicula of 
skeleton acerate, rarely acute. Interstitial membranes thin, translucent ; spicula 
acerate, slender. Sarcode abundant. 
Colour light grey. 
Hah. Tenby (Mrs. Brett). 
Examined in the dried state. 
Fortunately these cases of extreme paucity of characters are very few in number. 
