137 . 
S.A. NAT., VOL. XrV. 
August 31st. 19.'13. By Bernard C . Cotton (.ml F. K. Godfrey. 
mere film. This state continiics till the fifth and occasionally the 
sixth day after birth. The embryonic period lasts from thirty- 
live to forty days. Laca/.e-Duthiers observed a current of water 
jiassing through the shell from the opening at the smaller end. 
He dlscovx*red l^enlalAim at low water mark, where its presence 
was betrayed by a small groove in the sand, and he easily pro- 
cured 200 live specimens at a single low spring tide. They pre- 
fer certain spots, especially patches of coarse sand mixed wdth 
broken shells and interspersed with Zostera. The same observer 
kept some alive in a flask of sea water with a little sand for more 
than eighteen, months. It is much more active at night, being 
sensible of light. The foot acts as a piston in expelling at the 
other end the eggs and seminal fluid, as well as perhaps the faeces 
and exhausted w'ater. The point of a young shell is pear-shaped, 
and is broken off when too small to contain the terminal tube 
or process of the mantle; and this part of the shell is continually 
rubbed away as the animal increases in size, until at last it be- 
comes truncated, and a short pipe is formed with an oblique slit 
in front to accomodate the terminal tube. The slit is extended 
in certain species, although this distinctive character is confined 
to adult specimens. The inside of the shell is white as porcelain, 
and brilliant as varnish. 'Fhe periostracum is slight and easily 
abraded. The microscopical texture of the shell is scarcely dif- 
ferent from that of Patella. It is most complicated, being com- 
posed in a great measure of prisms, interlacing fibres, and anas- 
tomosing canals — not of cellular elements (Jeffreys). 
The class Scaphopoda includes but two families — the Dental- 
hdae and the Siphonodentaliidae. The distinctions between them 
are based upon (a) differences in the median tooth of the radula, 
(b) the form of the foot, (c) certain quite definite shell characters. 
The Dentaliidae has the median tooth of the radula twice 
as wide as long; a pointed conical foot surrounded by an epipod- 
ial process resembling a wingshaped sheath, which is interrupted 
or slit, like the break in a fold, on one side; a shell with greatest 
diameter at aperture. The shell is almost always, to some ex- 
tent, sculptured. 
In the Siphonodentaliidae the width of the median tooth of 
the radula is much less than double its length, generally less than 
its length. The foot lacks any epipodial processes^ and is either 
a slender vermiform organ or is expanded on the end into a sym- 
metrical disk with fluted or indented border. The shell, except 
in one restricted group, wholly lacks sculptural features, being 
smooth and glassy in texture, and it is generally contracted at 
the aperture. (Henderson). 
