MOLLUSCA, 165 
their dorsal surface scattered plumose branchize. Each of 
the tentacula is furnished with a large funnel-shaped sheath. 
The foot is very narrow, with a mesial groove, used in 
climbing up the stalks of sea-weeds. The mouth is placed 
at the base of the tentacula, and surrounded with a semi- 
circular lip. The tongue is in the form of a tubercle, witl: 
reflected points. The gullet is plaited longitudinally. The 
stomach is short and cylindrical, with a ring of hard, longi- 
tudinal scales. The liver consists of six unequal globules, 
and the bile is poured into the cardiac extremity of the gul- 
let. The Scyllea pelagica has been long known to naturalists, 
and appears to be very common in the equatorial seas, ad- 
hering to the stems of the Lucus natans. 
Genus THetuys.—Branchie forming a row on each side 
of the back, consisting of fringed processes, alternately larg- 
er and smaller. The body is ovate, with the cloak and foot 
continuous. The neck is distinct from the foot, and is nar- 
-row. Above, the neck is continuous with the cloak, from 
which arises a large semicircular expansion, used probably 
as afin. The margin of this expansion is fringed with nu- 
merous filaments, and on the upper surface, within the 
border, is a row of conical tubercles. The true tentacula 
are placed towards the base of this fin near the neck. Each 
of them consists of a small fleshy cone, striated across, with 
a semicircular sheath behind. The branchiz consist of a 
tapering, fleshy stalk, spirally twisted towards the summit 
with a series of filaments on one side. They are fourteen in 
number on each side, alternately and oppositely small and large. 
The anus opens in front of the third branchia on the right 
side. The orifice of generation is exhibited under the first 
branchia of the same side. In front of each of the larger 
branchiz, is a small cavity with a small filament in the cen- 
