UNIVALVES. DENTALIUM. 133 



One of tlie largest and most valuable species is the 

 D. elephantinum; it is often three or four inches long, 

 slightly curved, and has generally ten strong, elevated 

 ribs, which are encircled by dark green bands on a green- 

 ish ground; it inhabits the Indian and European seas. 



The D. aprinum and D. striatulum closely resemble the 

 D. elephantinum, but the former is usually much smaller, 

 and perfectly white. The latter is longer and narrower 

 in proportion, and the larger aperture is angular, and the 

 smaller very contracted and round; besides, it is supplied 

 with eight ribs and eight striae; and its color is more uni- 

 formly green. 



The D. rectum, though nearly allied to the D. ele- 

 phantinum, is a straight shell, and therefore easily dis- 

 tinguished from it. It is also adorned with doubled or 

 trippled longitudinal striae, which at the same time are 

 encircled with annular ones. The D.fasciatum is a small 

 species, finely striated, and encircled with four or five 

 brown bands on a greyish ground. 



Some species are striated annularly: such are the D. 

 politum, (which is finely pointed, solid, and often of a ro- 

 sy or pinkish color), the D. eburneum, and the D. en- 

 talis, which is an inhabitant of the Indian and European 

 shores, and is generally an inch and a half long, of a red- 

 dish or pale yellow color, and the tip often tinted with 

 orange or pink. 



Other species are smooth, or covered with striae, so mi- 

 nute that they cannot be discovered without the aid of a 

 magnifying glass. Of these, the D. pellucidum is an ex- 

 ample; it is of a horny or pale honey color, very nar- 

 row and thin, and does not effervesce in acids. It is an 

 inhabitant of the Northern seas, and about two inches and 

 a quarter long. 



