CLASS III. GASTEROPODA. ORDER I. CIRRHOBRANCHIATA. 5 
DENTALIUM, Linneus. 
Testa tubulosa, regularis, symmetrica, vel levis vel laqueata, plus mi- 
nusve arcuata; latere concavo ventrali, convexo dorsali; versus 
partem posticam sensim attenuata; extremitatibus perviis, apertura 
antica majore, simplici, plerumque obliqua, postica minore ; latere 
dorsali interdum fisso. 
The Dentalia were rightly placed by Linnzeus with the Mollusca ; not, 
however, from a knowledge of the true characters of their anatomy, but 
in accordance with his plan of referring to that division all animals dwell- 
ing in a tubular testaceous shell. The genus in question was thus asso- 
ciated with others of the most opposite character (Serpula, Teredo, e. g.), 
and as the anatomy of the Dentalia was still unknown both to Lamarck 
and Cuvier, they were removed by these authors with the Serpule to a 
place amongst the Annelides. Deshayes appears to have been the first 
to establish the important fact of their being true cirrhobranchiate mol- 
lusks, and he describes them as somewhat allied to the Patelle ; they are 
attached to their shell by a distinct muscle, and are furnished with an 
elongated subcylindrical foot, for the purpose of making their way in the 
sand. 
The shell of Dentalium is described as being tubular, regular, and 
symmetrical ; it is either smooth or fluted, and more or less curved ; 
the concave side being ventral, the convex dorsal ; it is also very much 
attenuated posteriorly, and both ends are open; the anterior aperture, 
which is the larger, is simple and generally oblique, and the posterior, 
which is also simple, is sometimes slit on the dorsal side. 
The fluted shell of the Dentalia is said to have furnished the design for 
the shafts of Doric columns. 
