SPIRULA. 



517 



tucket. The sliell is wliitc and pearly, coiled up in two ^'s- 755. 

 or three turns, which do not touch each other, some- 

 thing like a ram's horn. The surface exhibits constric- 

 tions, at short intervals, each of which corresponds to 

 an internal partition, so that the whole shell is divided 

 off into chambers, having a tube, however, at one side, so that the 

 whole are in communication. {Gould.^ 



The specimen figured is from the cabinet of E. R. Mayo, Esq. 

 It is from Nantucket. 



S. fragilis. 



