DENTALIIDA lll 
Crass SCAPHOPODA, 
Shell a hollow cylinder, open at both ends. Head rudimentary ; 
foot vermiform, lobulate ; nervous system simplified, resembling 
. that of the lamellibranchs. 
The shells of the Scaphopoda are immediately distinguishable 
from those of all other living mollusks by external form, being 
straight or slightly curved tubes, without spire. 
Famity DENTALIIDA. 
Shell tubular, symmetrical, curved, open at each end, attenu- 
ated posteriorly; surface smooth or longitudinally striated ; 
aperture circular, not constricted. 
Animal attached to its shell near the posterior anal orifice ; 
head rudimentary, eyes 0, tentacles 0; oral surface fringed ; 
foot pointed, conical, with symmetrical side-lobes, and an atten- 
uated base, in which is a hollow communicating with the 
stomach. Branchie 2, symmetrical, posterior to the heart; 
sexes separated. 
The tooth-shells are animal-feeders, devouring foraminifera 
and minute bivalves; they are found in sand, or mud, in which 
they usually bury themselves. 
Sars divides the Scaphopoda into two orders: I think that 
his distinctive characters are barely sufficient to be used in a 
subfamily sense. 
SuBFAMILY DHEHNTALIINA. 
Posterior aperture of the shell entire or with a ventral slit, 
provided with a supplementary tube. Foot trilobate. Edge of 
the lateral plates of the radula indistinctly dentate. (Order 
Scaphopoda, Sars.) 
Dentatium, Linn., 1758. 
Distr.—i5 sp. Universal. D. elephantinum, Linn. (ciii, 98). 
Animal with a short foot, anteriorly thickened and tripartite. 
Shell tube-like, gradually tapering posteriorly, longitudinally 
ribbed, margin of the aperture sharpened, posterior end with an 
internal, slightly projecting tube, which is provided with a dorso- 
ventrally elongated opening, the outer layer having a very slight 
emargination dorsally and ventrally. 
‘‘The Dentalium burrows in the sand by means of its conical 
foot, in a slanting direction ; the narrow end is, of course, upper- 
most, and is kept in communication with the air or water for the 
purpose of respiration. It feeds on foraminifera and other 
