PORIFERA OF THE L.M.B.C. DISTRICT. 993 
of dark grey colour. In April, 1889, I collected in the 
same cave several specimens of Seriola which were white 
with a slight greyish tint, and have kept their colour per- 
fectly well in strong spirit. The specimens have about 
the same dimensions as the original one, but they are 
flatter. Although the shape and colour of this sponge 
agree completely with those of Stelletta collings:, B., which 
I collected at the same time and in the same locality, still 
one may distinguish the two forms in the following way : 
Stelletia has a hispid surface; Seriola 1s smooth to the 
touch ; Stelleitta shows a cortex even ina rough vertical 
section made with the pocket-knife; Seviola does not. 
Curiously also a specimen of the new material was en- 
crusted by Suberites domuncula, and in the same way also 
one or two specimens of Stelletta collings:. The rest were 
not encrusted. Oscula and pores were not visible in the 
living specimens. 
The skeleton of Secriola compacta consists of megascleres 
and microscleres. ‘The former show the following forms: 
dichotrizna, orthotrizna, oxea, styl, strongyla, tylota. 
The dichotriena are very numerous, and are arranged 1m- 
mediately beneath the surface, with their cladomes directed 
towards the surface. The rhabdome measures from 0°36 
to 0°42 mm., the protocladus from 0°06 to 0°09 mm., and 
the deuterocladus from 0°037 to 0°45 mm. The ortho- 
trizena are far less numerous and slightly smaller than the 
dichotriena. They are also placed close to the surface. 
The oxea are the most numerous spicules, and are arranged 
in bundles, which take their origin in or immediately 
beneath the region of the trizna, and stretch vertically 
down through the whole depth of the sponge. The oxea 
measure 0°34 to 1°5 mm. by 0:009 to 0'026 mm. Amongst 
them we find a few stylote, strongylote, and tylote spicules. 
The microscleres are oxyasters, 0'025 mm. in diameter, 
