Vlll INTRODUCTION TO 



habitj in seasons of rest, of protecting itself by a network or vest of 

 marine fragments strung together by its byssal threads, 



Plate IX. 



Contains the shells of our PectenSj or Scallops, 1-16. The animals 

 swim like Lima, as above, and also spin a byssus. 



The class BracMopoda, 17-24, so named because what seem to be 

 organs of locomotion consist of a pair of coiled, ciliated arms, ends the 

 list of Headless Molluscs and their bivalve shells, 



Plate X. 



Class Pt&ropoda, 1-4, contains minute Mollusca, with glassy shells 

 variously formed, and wing-like expansions for swimming. 



Chiton, 5-17, or "Coat of Mail," which may often be seen incrust- 

 ing rocks, commences the Gasteropoda ; although seemingly fixed, 

 they are capable of locomotion, using the whole of the oval disc, 

 which may be seen on turning them over, for the purpose. The same 

 may be said of the " Limpet " tribe, Patella, 1-22. 



Plate XI. 

 This Plate commences with other forms of the Limpet tribe, Fissu- 

 rella, 1, 2, with a hole at the top ; Puncturella, 3, with a fissure near 

 the top ; and Emarginula, 4-6, with a slit at the margin. Haliotis, 7, 

 or pearly "Ear-shell," leads to the Trochida, or "Tops," 8-27. 



Plate XII. 



lanthina, 1-4, is genus of oceanic moUuscs, which are provided 

 with a beautiful floating apparatus, on which the female carries her 

 egg-bags. 



Nerilina, 5, and the Paludinidce, 8-11, live in fresh-water. The 

 animal of Palwdina is sprinkled all over with bright, golden specks. 

 The Littorince, or "Winkles," 12-24, are marine, and frequent the 

 shore among seaweeds. Lacuna, 25—32, belongs to the same family. 



Plates XIIL, XIV., 



Are small genera, various in their characters and habits, but reason- 

 ably included in the last family, Llttorinida. 



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