aed 
PORIFERA OF THE L.M.B.C. DISTRICT. Oley 
chondria suburea, and says, in regard to its habitat, ‘ It 
has the singular property of being attached only (so far as 
I have been able to ascertain) to old univalve shells, which 
it entirely invests.”” He mentions then that most of those 
shells were inhabited by hermit-crabs. Schmidt’s* defini- 
tion is similar, ‘‘ Suberites globosus, incrustans et invol- 
vens conchas, quas Paguri domos sibi elegerunt.” Mr. 
Higgin has already recorded specimens of this peculiar 
habit from Holyhead and Morecambe Bay, and I am able 
to add Calf of Man, where it was dredged on the ‘‘ Hyzena”’ 
expedition of April, 1889. But still this species does not 
seem to restrict itself exclusively to univalve shells in- 
habited by hermit-crabs, although those cases are the 
conspicuous and interesting ones. A sponge, apparently 
of the same species, was dredged on the above mentioned 
“ Hyena’ expedition of April, 1889, and also off Calf of 
Man. It encrusted a living Pecten opercularis, forming a 
thin layer (about 2 mm. in thickness) of greyish colour. 
I have found it also encrusting tetractinellid sponges, on 
Seiriola compacta, mihi, and on Stelletta collings:, B. As I 
shall state more fully on page 221, I erroneously described 
in my former report such an encrusting layer of Suberites 
domuncula as the ectosome of Sezriola. The upper portion 
of fig. 1, P]. VII., Vol. III., Proc. Liverpool Biol. Soc. may 
therefore be taken as a fairly correct representation of 
a vertical section through a Suberites domuncula. The 
thickness of that specimen was unusually small, only 
about 0°24 mm. The spicules of it are tylostyli 0°1 to 
0°38 mm. by 0:003 to 0:006 mm. They are arranged in 
bundles, and project for about one-half of their length 
through the ectoderm. The heads of the longer tylostyli 
are supported by the basal membrane. The figure also 
* Oscar Schmidt, ‘‘ Spongien des Adriatischen Meeres,” Theil i., p. 67. 
