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FIRST BOOK OF ZOOLOGY. 



illustration of the uses of the siphon. ■ In this particular 

 species, the siphon is much longer than the canal, and, when 

 the snail is crawling, the siphon is bent upward. As the 



Fig. 28.— A Sea Snail seen from below. — e, Eye ; m, Mouth ; s, Siphon. 



habit of this species is to crawl along partly buried in the 

 mud, the siphon, projecting above the level of the mud, 

 conducts the pure sea-water to the gills of the snail below. 

 Fig. 29 illustrates the appearance of this snail : 



A B C 



Fig. 29.— A, the Snail crawling upon the Surface of the Mud ; B, the same slightly buried ; (7, 

 the same nearly buried ; the Siphon, s, is seen curved upward. 



