GASTEROPODOUS M0LLU8CA OP BERWICKSHIRE. 35 



Order.— CYCLOBRANCHIATA. 



28. Patella. LinruBus, 



Shell generally ovato, sometimes oblong, more or less deprossedly 

 conical, rarely of a pyramidal form, concave beneath in proportion as 

 the veitex is donvex ; apex always more or less anterior, sometimes 

 very nearly central ; muscular impression elliptical, interrupted in front 

 where the head of the animal is placed. — See Sowerhy^s Genera. 



1 . P. vulgataj shell cinereous, bluish or greenish-grey, often rayed 

 with red or yellow bands, more or less distinctly ribbed and 

 striated longitudinally ; apex obtuse, sub-central ; base ovate, 

 the margin plain ; interior margaritaceous. Diam. from 1 to 2 

 inches. Dillw, Rec. Sh. 1032. 



Hah. Between tide marks abundant 



This common shell is subject to considerable variation in colour and shape : 

 sometimes it is extremely conic, often much depressed; sometimes 

 strongly ribbed and crossed with fine stria;, and often nearly smooth ; 

 of an uniform cinereous or greenish colour, or rayed with coloured 

 bands and streaks. 



The Limpet has two awl-shaped tentacula bulged at the base, where the 

 small sessile eyes are situated : mouth proboscidiform, armed with two 

 pairs of cartilaginous jaws of very unequal sizes, and with a tongue of 

 surprising length ; it is a narrow ribbon-like body fully 3 inches long, 

 of nearly equal breadth throughout excepting at the apex, where it is 

 somewhat dilated, the surface roughened with 3 rows of teeth ; the 

 side rows alternating with the middle one, which is quadrifid, while the 

 side teeth are divided only into two points : there is also placed along 

 each side of this remarkable organ a double row of cylindrical tubes 

 whose apertures look towards the base. The tongue is never pro- 

 jected outwardly, but is kept folded back, lying in the gullet and in- 

 testinal canal, and used probably as a rasp to grate down its fibrous 

 food. Foot plane, with an even margin : circunfference of the cloak 

 dusky or specked with dusky spots and furnished with numerous ten- 

 tacular filaments of unequal sizes ; and between the cloak and foot the 

 naked branchia) are visible. These form a thick delicate fringe around 

 the body between the foot and the ciliated margin of the cloak, and 

 are uninterrupted excepting on one side of the head or neck where 

 there is a channel that breaks the continuity, and leads obliquely to a 

 large cavity over the back, which has a wide and free communication 

 with the external atmosphere. The animal is usually stated to be 

 monoecious, and certainly there is no external difference among the 

 individuals ; but the observations of Mr J. £. Gray prove them to be 

 really bisexual. The females spawn in autumn or in the " back end,'' 

 when young and old, — the small and full grown, — are found pregnant 

 with numerous round eggs swimming in a transparent viscid fluid. 

 See Ann. Nat. Ilist. vol. i. p. 482. 



The walk of the Limpet is very slow and limited, and as they increase in 

 age and sizcy the unwillingness to move appears often to grow upon 



