BULLA DIPPER. 73 



Genus. BULL A* Plural, Bullcs. 



DIPPER OR WATER BUBBLE. 



Generic Character.-^ Shell univalve, convo- 

 luted, often without any spire, smooth ; J shape 

 suboval, inflated ; aperture longitudinal, gene- 

 rally the length of the shell, entire at the base ; 

 columella oblique, smooth. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



This genus is perhaps less accurately defined 

 than any other of the Linnsean genera : it contains 

 an assemblage of shells presenting a very varied 

 appearance ; indeed it seems as if it had been 

 formed to be a receptacle for including all the 

 species that could not find a place elsewhere. 

 The most distinguishing characteristic of the 

 Bulla is its gibbous or inflated figure, to which 

 it owes its name, signifying water bubble. One 



* Plate II. fig. 6, 8, 9. 



f It is hoped that Teachers who use these lessons will re- 

 collect that it is most important when the children are drawing 

 out the generic character, to bring before them a great variety 

 of shells, that they may group them according to resemblances 

 which they perceive, and under direction learn by observation, 

 their distinctive characters. 



J The Bullae are said to be smooth because their surface has 

 never any projections. 



