ie 
ae 
pero. 
a 
with descriptions of new Species. 345 
stout, fusiform, ;4.th of an inch long, much bent in the centre, 
and tapering towards the ends, which are sharp-pointed. 
The animal of this species when dry is snuff-coloured, and is 
readily distinguished from its congeners by its simple-formed 
spicula. When the shell in which it is concealed is broken 
across, the numerous, large, angulated chambers containing the 
lobes, separated only by thin walls, have much the appearance of 
honey-comb, lacking a little of its symmetry and perfect angu- 
larity. The C. nodosa is one of several species found in a large 
specimen of Tridacna gigas, and is evidently very destructive ; 
large portions of the strong ribs of the shell having given way 
in several places under the influence of this parasite. 
C. labyrinthica. Pl. XV. fig. 7. 
Sponge composed of an irregularly reticulated mass, the in- 
terlacing being exceedingly minute, and so intricate that it is im- 
possible to determine the order of the parts: papille not very 
numerous, minute, without apparent order. Spicula numerous, 
fusiform, ,4=rd of an inch long, rather stout, nearly cylindrical, 
slightly and regularly bent from end to end, with each termi- 
nation suddenly brought to a sharp point. 
When dried this species is of a pale straw colour: it occurs 
in Tridacna gigas, to the shell of which it is very destructive. 
Several specimens have occurred ; one of them has sunk upwards 
of an inch deep into one of the ribs of the shell, and has extended 
its ravages four or five inches in length and nearly two in breadth, 
passing, in fact, from side to side of the nb, and giving to the 
entire substance the appearance of the central cellular structure 
of bone; and this resemblance is rendered the more perfect on 
account of a thin layer of the surface being left almost sound. 
Genus THoosa*, 
Sponge branched or lobed, buried in calcareous bodies; the 
interior with anastomosing tubes, and devoid of spicula ; the sur- 
face with a crust of nodulous, crystalline bodies composed of 
silex. 
This genus by its general form and habit is closely related to 
Cliona, from which it differs chiefly in the character of the sili- 
ceous bodies on the surface, and in the absence of spicula from 
the interior. Two or three species have occurred; they are all from 
the tropics, and vary considerably in form; one or two of them 
have radiating spicula mixed with the siliceous bodies of the 
surface. 
T. cactoides. PI. XIII. figs. 1 & 2. 
Sponge branched, strongly lobed, regularly and widely ana- 
* A sea-nymph. 
