with descriptions of new Species. 335 
terminal twigs regularly bifurcating, the branches have conse- 
quently a dichotomous arrangement : papille placed rather far 
apart, small, of equal size, and arranged in a single row along the 
branches, the direction of which they distinctly indicate on the 
surface of the matrix. Spicula of two kinds; the larger about 
7;th of an inch in length, generally a little bent, stout and in- 
clining to fusiform, with the pointed end gradually tapering ; the 
opposite extremity provided with a rounded head, somewhat ellip- 
tical, and merging imperceptibly into the shaft. The smaller 
spicula are about ird the length of the larger ones, and are less 
stout ; they bend gradually in the centre, from whence they taper 
to a fine point at each end. 
I have seen only one specimen of this species ; it is i Pecten 
maximus, most probably from Orkney, and extends from the beak 
to the ventral margin. The spicula somewhat resemble those of 
C. corallinoides, but are considerably stouter ; and though the 
heads are large and well-formed, they are not so distinctly marked 
as in that species; and the smaller ones bend less abruptly : the 
character of the branches is also remarkably different. 
The walls of the excavations of this species are rather finely 
punctured. 
C. muscoides. Pl. XV. fig. 11. 
Sponge formed of numerous delicate, much-divided, closely 
and irregularly anastomosing branches, with the terminal ones 
very slender and composed of an open network; the principal 
branches about ;1,th of an inch thick, and distinctly seen rami- 
fying throughout the general interlacement of the sponge: pa- 
pillee small, very numerous, approximating, and where the ana- 
stomosis is extensive, without apparent order ; towards the ter- 
minal branches however they run in rows, and betray the course 
of the branches on the surface of the shell in which the specimen 
is buried. Spicula of two kinds, one with heads, the other with 
both ends pointed; the former, measuring ;i5th of an inch in 
length, are generally straight, proportionately stout, and with 
two globular heads, one terminal, though not always perfectly so, 
and one placed at a little distance down the shaft; occasionally 
there is an additional head a little way below the second; from 
this end the shaft tapers gradually to a sharp point at the oppo- 
site extremity, towards which there is frequently a slight bend. 
The other kind of spicula are fusiform and as stout as those with 
heads, but only half their length ; they taper gently to both ends, 
which are finely pointed, and bend abruptly in the centre, where 
there is frequently a nodulous swelling ; there is also occasionally 
another indistinct nodule or two on each side of the centre one 
and at some little distance from it. 
