9 
FAMILY L— METRIDIADiE. 
{No European species.) 
FAMILY IL— SAGARTIAD^. 
I have thought tit to associate in this group those genera 
of the Tribe, which have the following characters : — They 
do not deposit a coraUum. They have a broad base, capable, 
at the pleasure of the animal, of firmly adhering to foreign 
bodies, such as rocks, stones, and shells ; or of being used 
as a foot, on which to creep, somewhat in the manner of a 
snail. They have always simple, smooth tentacles, arranged 
in (generally) unintemipted circles at the margin of the 
disk, but often encroaching far upon its surface. Their 
body is for the most part pulpy or fleshy, generally lubri- 
cated on the surface with copious mucus ; its exterior is 
often studded with sucking cavities, hicli have the power 
of adhering to foreign bodies, by the formation of a vacuum 
within the cavity, its muscular edges being appressed by 
the weight of the superincumbent atmosphere and water. 
The margins of these cavities do not rise into conspicuous 
warts when inactive. The integument is pierced with 
loop-holes {cinclides ), — special orifices, through which are 
emitted and retracted fleshy cords {acontia), which liave 
their origin in the membranous partitions of the body- 
cavity. These arc filled with capsules {cnidce), which arc 
generally chamhered, and which shoot a very short, but 
densely-armed wire {ecthormm). 
