7O THE GASTROPODA 
forms the posterior extremity of the foot bears a pair of tentacles 
which are sometimes bifurcated, and in Phos there is a single filament 
in this position. In Pterotrachea the foot terminates posteriorly in 
along filiform contractile appendage, bearing several annular vari- 
cosities. In Cymbulia the posterior lobe of the foot also ends in a 
long whip-like appendage. (6) On the sides of the foot, at about 
the middle of its height, there is often a ridge, the epipodium, 
extending from the head to the posterior end of the foot. This 
ridge is specially well developed in various Rhipidoglossa (Fig. 130, 
VIII), and may bear appendages of greater or less length, sensory 
organs, and pigment spots, the last-named, however, showing no 
trace of the structure of eyes. The anterior part of the epipodium 
Fic. 46, 
Rostellaria rectirostris, animal and shell, right-side view. a, snout or rostrum ; }, cephalic 
tentacle; c, eye; d, anterior part of the foot ; e, posterior (operculigerous) part of the foot; f, 
operculum ; h’, anterior canal of the shell, occupied by the pallial siphon. (From Lankester, 
after Adams.) 
generally forms a cervical lobe, which exhibits a characteristic 
asymmetry in certain Trochidae. The epipodium is found also 
in Litiopa, the Rissoidae, Narica, Janthina, ete., and a portion of 
it is represented by the cervical lobes in Paludina, Ampullaria, 
and Calyptraea. 
The surface of the foot is normally furnished with a large number 
of unicellular mucous glands, and very often these cells are specially 
accumulated in invaginations of the integument, distinguished as 
pedal glands. The most important of these invaginations are—(1) 
The anterior groove of the foot (Fig. 144, IV), into which open the 
so-called labial glands: it is often continued into a fairly long canal. 
This anterior pedal gland is very generally present in the aquatic 
creeping species of Streptoneura and Opisthobranchs ; it secretes 
the mucus which lubricates the surface of the foot, and is auxiliary 
to creeping whether it be on the bottom of the sea or on the 
