16 
MARINE FAUNA OF ST. ANDREWS. 
portions as possible; but this is their only approximation to 
each other; in their other characters they differ to a con¬ 
siderable extent. The colour of H. rcgxdaris in the dried 
state is milk-white ; that of H. M l Intoslni is nut-brown. An¬ 
other important difference is, that while the skeleton of H. 
regularis is remarkable for its symmetry, that of II. M l Intoshii 
is irregular to a very considerable degree.” 
This form is not uncommon on the under surface of stones 
in tide-runs and somewhat muddy pools not far from high- 
water mark at the East Rocks. Its greyish brown colour, 
smooth surface, and prominent, well-defined oscula distinguish 
it at first sight from its allies. 
Halichondria incrustans , Esper; Bowerb. vol. ii. p. 249. 
Occasionally found under stones near low-water mark, 
especially at the East Rocks. It forms a thickish crust; and 
the spicula very much resemble one of the knobbed walking- 
sticks which taper from above downwards. 
* 
Suborder III. Keratosa. 
Chalina oculata, Pallas; Bowerb. vol. ii. p. 361. 
Thrown in great profusion on the West Sands after storms ; 
and small specimens are also found under the ledges of rocks 
near low-water mark. The shape of the specimens varies 
much : some are flattened and much divided into branches of 
various sizes, either narrow or broad; others have their 
branches matted together so as to form a connected and 
somewhat coarse “gorgonian ” appearance, more or less sepa¬ 
rated at the tip. In some the branches arise mostly from one 
side of an unbroken prolongation of the sponge-tissue. One 
, grows on a valve of Mytilus modiolus , and has a mass of 
Halichondria panicea round a branch at its base. Another 
envelops the stem and branches of Delesseria sanguinca , the 
leaves of which appear here and there from the centre of 
the sponge. Many are attached to small rolled stones. 
