SHELLS. 



53 



Harp Shell (JJafpu ventricosu). 



home his hand was caught between shell and rock, and so firmly- 

 held by the animal that he could not escape the rising tide, and 

 was drowned. 



The pearly lining of the abalone is richly shaded with all colors 

 of the rainbow, an opalescent green often predominating. The 

 mother-of-pearl is composed of 

 undulating layers. The irides- 

 cence is caused by minute lines 

 reflecting different spectra. 



Some members of the snail 

 family, with their world-wide 

 reputation for slowness, have 

 made amazing progress in the 

 ascending scale. They have gone 

 so far as to develep from the 

 gills, with which they breathed in the water, lungs suitable for 

 air-breathing, and have come to enjoy the pleasures which a life 

 on terra firma affords. You can find them in the woods or in 

 your garden, thrusting out their inquisitive little heads and in- 

 vestigating everything with their eye-tipped feelers. Some snails, 

 after trying the experiment of a land life, have decided that on 

 the whole a water life is preferable, and gone back to live there, 

 where they have developed gills again, but of a different kind 

 from the original ones. 



There are sea snails, pond and river snails, as well as land 

 snails. Many of them are carnivorous and can bore into other 

 shells with their lingual ribbons. The hole usually strikes a 

 muscle, when the shell gapes open, and his snailship enters and 

 devours his prey. 



Some kinds of snails, especially the land group, can live for a 

 great length of time without food. A snail was fastened to a card 

 and put in the British Museum in 1846. Four years afterward a 

 discoloration appeared on the card, showing that he had been 

 moving about. He was taken out, immersed in warm water, and 

 was soon quite lively. 



In creeping about, the snails always leave a track of mucus, 

 which glistens when it is dry. It is in this mucus that they 

 immure themselves for their long winter's nap, sometimes making 

 several layers or partitions over the opening to the shell. 



In the middle ages snail shells were worn as amulets, protect- 

 ing the wearer against certain diseases as well as witchcraft. 



Prof. J. S. Kingsley says of one North American species {Helix 

 harpa) : " In motion it is exceedingly graceful, at times poising its 

 beautiful shell above its body and twirling it around, . . . again 

 hugging its pretty harp close to its body." 



The shells of the common wood snails are quite transparent 



