ACHATINA. ONCHIDIUM. 



41 



Fig. 26. 



AMBRETTE. 



to lodge the entire animal (fig. 26) : the shell 

 is thin and translucent, and obtains its name 

 from a supposed resemblance to amber: they 

 live upon plants that grow along the margins 

 of rivulets and brooks. 



19. The genus of 

 ACHATINA (fig. 

 27) is composed of 

 large snails, which, 

 in warm countries, 

 feed on shrubs ; they have an oblong 

 shell with the opening wider than it 

 is high, without a thickened lip, and 

 truncate at the extremity of the colu- 

 mella, a disposition somewhat analo- 

 gous to that of the shell of most ma- 

 rine gasteropods. 



20. The family of PULMONEA 

 AQUATICA have but two tentacles 

 (fig. 18, page 33); their mode of 

 respiration obliges them to come fre- 

 quently to the surface of the water to 

 breathe : they cannot keep at great 

 depths, and they ordinarily live in 

 fresh waters, or near coasts. 



21. As in the preceding family, we find here mollusks without 

 a shell, and others that are provided with one : the first form thi 

 genus of Onchidium (fig. 28), which have a very straight anl 

 very extensible elongated body ; they inhabit the fresh waters of 



Fig. 27. ACHATINA. 



Fig. 28. ONCHTDIUM 



19. What shells form the genus of Achatina? (pronounced a-ka.te.na). 



20. What are the characters of the family of Pulmonea Aquatica. 



21. What are the characters of the genus Onchidiam ? 



4* 2U 



