126 UNIVALVES. 



Genus DENTALIUM.* PZamZ, 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 

 derived 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 orna- 

 mented. One of the largest, called, Dentalium 

 Elephantinum is often three or four inches long, 

 and is strongly marked with longitudinal ele- 

 vated ribs. One species is so minute that it is 

 scarcely discernible by the naked eye, and resem- 

 bles a small bristle. 



There is but little known of the inhabitant of 



* Plate VI. figure 6. 



