352 



that's it ; 



Limpets are so called from the resemblance 

 of their shells to a little plate (patella). They 

 are herbivorous, feeding upon sea weeds, which 

 they reduce with their long ribbon-shaped 

 tongues, which are from two to three inches 

 long., with a spoon-like extremity, armed along 

 their whole length with transverse rows of 

 sharp hooked teeth. Sea weeds thrown upon 

 the shore will be frequently found to bear 

 murks of the depredations of these creatures. 



The periwinkle, 18, is one of 

 the g aster opo clous molluscs, so 

 called because of their habit of 

 creeping, using the belly as a 

 foot. It is well-known as the 

 common shell-fish hawked about 

 the streets, affording a savory 

 relish to humble appetites. Its 

 eyes, unlike those of the land 



18 



1166. 



snail, are placed at the base of 

 the tentacula instead of at their 

 extremities. Their tongues are 

 long, and armed with transverse 

 rows of teeth. Members of 

 this group inhabit all regions of 

 the sea, but by far the greater 

 number of them live near the 

 shore, and a very considerable 

 portion of them are found be- 

 tween tide marks. 



Swedish peasants say that when periwinkles 

 creep hi^h up the rocks, ic indicates a storm 

 approaching from the south; and the Norwe- 

 gians say that when they creep in towards the 

 coast, it indicates a land-wind, and a calm 

 in-shore. 



They live upon sea weeds that 

 grow upon the rocks which they 



11G7. 



inhabit. The shells of some 



the species, 

 and acute 

 than that of 

 the common 

 periwinkle. 



Some of these 

 shells are sym- 

 metrical, consist- 

 ing of more pieces 

 than one ; others 

 are symmetrical, 

 but formed of a 

 single piece; and . 

 there are also 

 some non-sym- 

 metrical, which, 

 in species where 

 they are very con- 

 cave, and where 

 they grow a long 

 time, necessarily 

 produce an ob- 

 lique spire, 19. The part on which the cone 

 is rolled is called the columella, or pillar: this 

 is sometimes solid, and sometimes hollow. 

 When it is hollow, the upper end of it is named 

 the umbilicus. Shells with an elonnated or 

 projecting spire, are called turbinated When, 

 on the other hand, the whorls remain nearly 

 on the same plane, and are not enveloped one 

 within another, the shells are called discoid. 

 When the upper part of each whorl envelopes 

 the preceding ones, the spire is said to be con- 

 cealed. That part of the shell from which the 

 anim il comes forth is called the aperture. 

 When the spire is elongated, it is directed to 

 the right of the animal when it creeps; but 

 in a small number it is directed to the left; 

 and when this occurs, the shells are called 

 reversed, or left-handed. 



The mollusca, speaking of them 

 generally, are found abundantly 

 distributed over every part of 

 the globe — in seas, rivers, sands, 

 forests, and plains. Their num- 

 ber is incalculable, and the form 

 of their bodies is beyond every- 

 thing extraordinary : — 



" Where the pool 

 Stands mantled o'er *rith green, invisible 

 Amid the floating verdure, millions stray ; 

 Each liquid too, whether it pierces, soothes, 

 Inflames, refreshes, or exalts the taste. 

 With various forms abounds. Nor is the stream 

 Of purest crystal, nor tne lucid air 

 (Though one transparent vacancy it seems) 

 Void of its unseen people. 

 Let no presuming impious railer tax 

 Creative Wisdom, u aucht was formed 

 In vain, or not for admirable ends. 

 Shall little hauerhty ignorance pronounce 

 His wnrks unwise, of which the smallest part 

 Exceeds the narrow vision of her mind?" 



