216 
LIMNiEAD^. 
Tentacles compressed^ triangular^ with an auricle 
at the base ; jaics three^ papilliform (fig. 53.); 
the eyes are placed on a small lateral lohe on the 
side of the base of the triangular truncated ten-- 
tacle ; shell conical^ hoodlike^ apex subspiral, 
(Ancyllna.) 
3. Anctlus. (River Limpet.) 
Animal conical ; body attached to the foot the whole 
length, and covered with an ovate, conical, 
Fig. 52 . simple shell, which is bent to the 
right, with a central posterior 
rather obliquely recurved tip; 
the cavity with a lunate sub- 
marginal scar, interrupted on the 
Ancylm fiuviatilis. left side, for the passage of the 
air-tube to the lungs. The aperture of respira- 
tion and vent are on the left side. (fig. 52.) 
On the tongue of Ancylus there are thirty similar 
lateral teeth in a straight line on each side of the 
central tooth ; and then there is a curve through a 
series of six more teeth, where a trifling change in 
their form occurs. 
The Jaws of Ancylus fluviatilis 
magnified. 
ot, Upper jaw ; 5, Lateral jaws united ; c, The 
mouth closed. 
So called from the close connection by which the 
circumference of the shell is fixed to its attachment ; 
or perhaps from the conical point, resembling the 
