GENERA OF SHELLS. 



ANNULATA 



Forms the Ninth Class of Lamar cW s Division 

 of the Animal Kingdom. 



SEDENTARY ANNULATA 

 Compose the third Order of this class. 

 They are usually found attached to marine 

 substances, and inhabit membranous or horny 

 tubes, more or less encrusted with grains of 

 sand and fragments of shells. 



DORSALIA. 



Arenicola — has no shell. 



SiLiQ^uARiA. Shell tubular, irregularly con- 

 torted, tapering posteriorly, sometimes spiral 

 at base, open at its anterior extremity, having 

 a longitudinal, subarticulate fissure throughout 

 its length. 



S. anguina, muricata, laevigata, terebella, lactea, lima, 

 spinosa. 



