126 UNIVALVES. 



Genus DENTALIUM.* P^mZ, Dentalia. 



TOOTH OR TUSK SHELL. 



Generic Character. Shell univalve, gradually 

 tapering, straight or slightly curved, resembling 

 a tooth without any internal partition, open at 

 both ends. 



OBSERVATIONS ON THE SHELL AND ITS 

 INHABITANT. 



The shells of this genus are easily known by 

 their very simple construction ; they all more or 

 less resemble a miniature tusk, and the name de- 

 rived from the Latin dens, a tooth, refers to this 

 form. There are but few species, and these vary 

 principally in external appearance, in magnitude, 

 in the degree of curvature, and in the ribs or 

 grooves with which some of them are ornamented. 

 One of the largest, called, Dentalium Elephanti- 

 num is often three or four inches long, and is 

 strongly marked with longitudinal elevated ribs. 

 One species is so minute that it is scarcely dis- 

 cernible by the naked eye, and resembles a small 

 bristle. 



There is but little known of the inhabitant of 



* Plate VI. figure 6. 



