TONGUE OF THE LIMPET. 293 



upon the thinnest part of the shell, and is perfectly circular, of a 

 champhered form, being wider towards the outward side, and so 

 perfectly smooth and regular as to have all the appearance of 

 the most beautiful work of an expert artist. It became a 

 matter extremely desirable to preserve the mussel, and it seemed 

 practicable to extirpate the buccinum. But after we had picked 

 up and destroyed many barrels of them, their extirpation was 

 at length given up as a hopeless task. The mussels were con- 

 sequently abandoned as their prey ; and, in the course of the 

 third year's operations, so successful had the ravages of the 

 buccinum been that not a single member of the imported 

 mussel colony was to be found upon the rock." Thus the 

 engineer, whose skill and perseverance had gained so proud a 

 triumph over the waves of the stormy ocean, was defeated by 

 an ignoble whelk. 



In the genera which have no proboscis, the tongue, acting as 

 a prehensile and rasping or abrading organ, is frequently of con- 

 siderable length ; thus, in the Ear-shell, it is half as long as the 

 body, and in the common Limpet even three times longer than 

 the entire animal. From 



the two cartilaginous (y^^^^^d i®L a 



pieces (b b), placed on ^nk ^Sl^C''" 



each side of its root, arise )| tfpz^iZZ^^'^'^^sifmw 



the short and powerful r/ \SL^ C^^-jb^ 



muscles which wield the ^s. "iN W^^^\ 



organ. The surface of \v_ ^/ Pfcf^j 



this curious piece of x a 



mechanism, a magnified Limpet's tongue. 



view of which is given 



at B, is armed with minute, though strong, teeth, placed in 

 transverse rows, and arranged in three series; each central 

 group consists of four spines, while those on the sides, con- 

 tain but two a-piece. It is only at its anterior extremity (d), 

 however, that the tongue, so armed, presents that horny 

 hardness needful for the performance of its functions, the 

 posterior part being comparatively soft; so that, probably 

 in proportion as the anterior part is worn away, the parts 

 behind it gradually assume the necessary firmness, and ad- 

 vance to supply its place. In the upper part of the cir- 

 cumference of the mouth, we find a semicircular horny 



