PERIWINKLES WHELKS. 21 



way in which it works, and the effectiveness with 

 which the vegetation is cleared away before it, all 

 strike the mind as both wonderful and beautiful." 



I have classed the Limpet (Patella vulgatd) with 

 the Periwinkle, as being equally useful as a tank 

 scavenger. He is not inferior in interest as an object 

 of study, while as an ornament, no comparison can 

 be instituted between the two. Indeed, few occup- 

 ants of the Aquarium are more pleasant to look at 

 than a Limpet, as he glides along, with a whole forest 

 of weeds and frondlets growing on his back. 



Our familiarity with this mollusc it is one of the 

 commonest on the sea-shore is apt to make us 

 imagine there is nothing wonderful or peculiar in his 

 structure. A little acquaintance with zoology will, 

 however, soon undeceive us. Indeed, almost every 

 part of the construction of this animal is calculated 

 to excite our wonder. Who, for example, would 

 suppose that the tongue of the Limpet was so ingeni- 

 ously framed, that it was a ribbon-shaped organ fully 

 three inches in length, that its teeth were spinous, 

 and that there were three rows of these ; that further, 

 the teeth of the middle row were cut into four points, 

 and those of the external rows, (which are not exactly 

 opposite to or continuous with those of the middle 

 series, but alternate with them,) were cut into two 

 points only 1 * 



This curiously toothed tongue " is never protruded 

 beyond the margin of the lips. It seems to be used 

 * Vide Gosse, "Nat. Hist." 



