SHELLS WITHOUT CANALS 217 



alone, since you will be likely to break the shell if 

 you persist in your endeavor. In some countries 

 limpets are eaten, and vast numbers are used by the 

 fishermen as bait. Notice carefully the broad foot, 

 the mantle and gills, and the short head with its 

 mouth and tentacles. If a specimen is dissected the 

 lingual ribbon may easily be obtained from the 

 mouth, and with a low power microscope the beauti- 

 ful rows of teeth may easily be made out. After the 

 animal has been removed from the shell observe the 

 horseshoe-shaped muscle-scar. 

 Acmcza patina^ Esch., the 

 Plate Limpet, Figure 211, is 

 one of the most common 

 kinds. The shell is oval and Fig.2u 



flattened, with an indistinct 



apex near the center. From this radiate line striae, 

 which are often quite indefinite. The shell is also 

 often partly overlaid with brownish sea-growths. 

 Young specimens are sometimes prettily checked with 

 brown and green. Within the shell there are various 

 markings of brown and bluish-white, with a dark ring 

 around the edge. The common length of the shell 

 is from an inch to two inches. 



Acniaea pelta^ Esch., 



the Shield Limpet, Figure 



212, is more conical and 



pointed than the last, and 



.-. ,,. the outside of the shell has 



rig. 112, 



about twenty-five blunt, 

 radiating ribs. Externally it is gray or striped, and 

 is sometimes very beautiful: the inside is mainly 



