LIMPETS. 39 



with great force, and submit to have their shells 

 broken before they will yield. In some countries 

 they are eaten, and also vast numbers are gath- 

 ered as bait by the fishermen. Notice carefully 

 the broad foot, the mantle and gills, the short 

 head and tentacles, and the horse-shoe shaped 

 muscular impression, inside the shell. 



Acmaa patina, Esch., Plate Limpet, Fig. 6. 

 PI. X, is oval, flattened, with the apex nearly 

 central, and more or less distinct, radiating striae. 

 Externally it is dark, often overgrown with moss 

 &c; internally, near the edge, there is a dark 

 rin<r; often broken into blocks, then a broad, blue- 

 white enameled space, and within the muscular 

 impression is a patch of brown. Length of shell, 

 one to two inches. 



Acmtm pelta, Esch , Shield Limpet, Fig. 4, 

 PI. X, is more conical and pointed,, with about 

 25 blunt ribs, sometimes obsolete. The outside 

 is brownish or striped ; the inside white, with a 

 narrow, dark thread round the edge, and a brown 

 patch in the center. At Duxbury lieef, in Marin 

 Co., I found some old specimens, with very thick 

 shells, living in deep depressions which they had 

 made in the rock. A small, black, conical shell, 

 supposed by Carpenter to bean abnormal growth 

 of the young of this species, is now known as 

 Acmma Asmi, Midd. 



Acmcea persona, Esch., Mask Limpet, Fig. 5, 

 PI. X, can easily be distinguished from the pre- 

 ceding species, by the posterior position of the 

 a}: ex. The ribs on the front of the. shell are 

 prominent, but rough and irregular. Its outside 

 color is brownish, or mottled; internally it resem- 



