CHARACTERISTIC DEEP-SEA TYPES. — SPONGES. 179 
form: a thick, coarse, smooth sheet, with stout branches, either 
round or angular. 
One of the most abundant sponges 
is the small Liadiella sol (Fig. 545), 
which extends to over 1,000 fathoms 
in depth. Its general appearance is that 
of a segment of a sphere surrounded by 
a fringe of needles, with a layer of larger 
needles radiating from the centre of 
N 
the disk and forming the base. Fig. 545. — Radiella sol. 2. 
