UNIVALVES DENTALIITM. 



li:^ 



Benticulata. 



Nodulosa. 



Augusta. 



Injequalis. ' 



Minuta. 



Conspersa. 



Rubescens. 



Sanguinea. 



Ventricosa. 



Triradiata. 



Tenuis. 



Melanozonias. 



Etfusa. 



Punicea. 



Rufescens. 



Dimidinta. 



Lactea. 



PyramidaUs. 



Bicolor. 



Erythrocej)hala. 



Verrucosa. 



Contaminata. 



Atrata. 



Candicans. 



Succincta. 



Pusilla. 



Flavescens. 



Antiquata. 



Galeata. 



Personata {Radiated-onmkL) 



DENTALIUM.— Tooth or Tusk-Shell. 



Animal — aTerebella: Shell Mnivahe, tuhulaVy straight, 

 or slightly curvedt with an undivided cavity open at both 

 ends. 



Of this singular genus there are but twenty-two species ; 

 in their general form they are very similar, and represent 

 an excellent fac-simileofan elephant's tusk in miniature. 



The chief variations which they seem subject to are : 

 in magnitude, and in the number of ribs and grooves 

 that some of the species are supplied with; some trijfling 

 distinction may also be made with regard to the de- 



