DENTALIUM. 235 



tliougli he existed not, and his Hfe is no more than a 

 dream." 



CIEEOBEANCHS. 



Another class of beings, such as men 

 In olden times knew not, for none had sought, 

 With curious ken, to trace each small design ; — 

 Though small, yet perfect, and befitting well 

 Some destined pm'pose. 



The breatliing organs pertaining to this order are cir- 

 rhous, symmetrically divided into two equal tufts of soft, 

 flexible, club-shaped filaments, attached to a pedicle on the 

 neck. Their structure is very peculiar, and is apparently 

 adapted for a twofold purpose; — that of conveying the 

 vital oxygen to the blood, and that of drawing a current 

 of water by the active movements of their filaments. 



One genus is alone recognized as pertaining to this 

 order. 



The shell of the solitary genus Dentalium is described 

 as being tubular, regular, and symmetrical; it is either 

 smooth or fluted, and more or less curved, the concave side 



