140 

 CHAPTER XXXVI. 



OF THE DENTALIUM. GENUS XXXIII. 



DENTALIUM. 



'•Animal a Terebella. Shell univalve, tubular, straight, one-celled, both 

 ends pervious." — Linn. 



1 HIS genus is very well defined, and easily distinguished from 

 every other. 



These shells are a little tapering, but nearly cylindrical, gene- 

 rally open at both ends, and a little bowed or bending ; several 

 species have a certain number of ribs or ridges running the 

 whole length of the outside : these Linnaeus calls angles. 

 D. stn'atuluin has eight ribs (/. 1 29), and is said to be octan- 

 gulattim ; D. elephantinum with ten is termed decemangulatutn ; 

 the internal cavity is generally round. 



The animal is nearly similar to some species of Serjmla. 



Linnaeus has described 8 species, Gmelin has added 13, and 

 Dr. Turton 1. Total, 22. 



Lamarck lias not divided this genus, but arranges it with 

 his Vermes, after Terebella, Amphitrite, and some of the Ser- 

 pnlfc ; and describes it as an animal contained in a testaceous 

 solid tube, slightly arched, and open at both ends (see Denta- 

 Inan striotnlurn, pi. 9. /. 129). 



