448 DENTALIADiE. 



the shell. For other points of difference and of detail, we 

 refer our readers to the papers cited. 



DENTALIUM, Linn^us. 



Shell symmetrical, cylindrical, forming a long tube, its 

 anterior orifice open, without constriction, to the greatest 

 breadth of the shell, the posterior extremity attenuated 

 and perforated ; surface smooth or annulated, or longitudi- 

 nally ribbed or striated, or with decussating strise. 



Animal elongated, attached to the shell near its hinder 

 extremity ; head rudimentary, eyeless, and without ten- 

 tacles, cirrhated on the lip : mantle circular, thick and 

 fleshy in front, thin posteriorly, capable of investing the 

 entire frontal part of the body ; foot placed centrally and 

 anteriorly, consisting of a pointed cone, flanked by two 

 symmetrical side lobes, and mounted on a long pedicle, 

 grooved on both surfaces, centrally hollow, the cavity com- 

 municating with the stomach. Branchiae and heart as 

 already noticed. Sexes probably united. Main mass of 

 the nervous system in the form of four nerve ganglions, 

 connected to form a collar around the oesophagus. Stomach 

 furnished with a strong gizzard anteriorly, vent subcentral. 

 Lingual membrane (according to Loven) broad, ovate, 

 each section with a single-toothed rachis, flanked on each 

 side by a single lateral. 



These mollusks are animal-feeders, devouring with 

 avidity Foraminifera, and sometimes small bivalves. Mr. 

 Clark has found species of as many as eleven distinct 

 genera in the pouches on the two sides of the mouth, or in 

 the stomach of D. Tarentinum. On the affinities of this 

 genus, he remarks " the symmetrical subventral position 

 of the branchise, the posterior flow of water to them, and 



