SPONGES. 
15 
interwoven stalks of Corallina officinalis and Fuci. Near the 
Maiden Rock splendid specimens are found incrusting a square 
foot or two of rock in some of the quiet pools. It also abounds 
on the backs of crabs, such as Ilyas araneus and Inachus 
dorynchus , covering the former so completely that it can 
scarcely be recognized except by its legs ; and besides the pro¬ 
minent oscula of the sponge, on this complex back are gaps 
for Balani , shells, and seaweeds. On the carapace of the latter 
species it forms a thinner coating, but is likewise grouped in 
little nodules on the legs. A mass as large as a good-sized 
apple surrounds the stem of Chalina oculata ; and it is a com¬ 
mon envelopment of various stones, mollusks, seaweeds, and 
tangle-roots. The usual colours of the sponge are yellow, 
brown, purple, green, and grey. In the interstices of the 
masses thrown on shore at the West Sands are to be found mul¬ 
titudes of marine animals, besides incorporated shells ; and the 
fine patches at the East Rocks are favourite feeding-grounds of 
Doris tuberculata. The forms of the spicula of this species 
are variable, some being much curved like a stretched bow, 
a few more or less inasquiacerate vermiculoid, besides, of 
course, the ordinary diagnostic spicula. The odour emitted 
on tearing it from the rock is characteristic, but causes no 
sneezing. 
Halichondria , n. s.* 
The following is Dr. Bowerbank’s description :— u Sponge 
coating, thin. Surface smooth and even. Oscula more or 
less elevated, dispersed, margins thin. Pores inconspicuous. 
Dermal membrane aspiculous. Skeleton very irregular, rete 
mostly unispiculous, occasionally bi- or trispiculous; spicula 
acerate, short and stout. Interstitial membranes aspiculous. 
“ Colour in the dried state light nut-brown. Examined in 
the living and dried states. 
u The nearest alliance with the known species of the first 
section of our British Halichondrioe is with II. regidaris. The 
spicula of the two species are as nearly alike in size and pro- 
* Dr. Bowerbank has courteously named this species II. M l Intoshii, 
Bowerb. 
