424 PHYLUM MOLLUSCA. 
Class II. SOLENOGASTRES 
The members of this class are worm-like animals, in which the 
mantle envelops the whole body and bears numerous spicules, but no 
shell. It is somewhat doubtful if they are Molluscs at all. There are 
two families—Neomeniidze and Cheetodermidee. 
Of Neomeniide, six genera are known, e.g. Meomenia and Pro- 
neomenta, They have a longitudinal 
pedal groove, an intestine without 
distinct digestive gland, two neph- 
cbc wea ridia with a common aperture, and 
ae ip hermaphrodite reproductive organs. 
VY, The Cheetodermidz, represented by 
EF one genus Chetoderma, are cylin- 
ry drical in form, without a pedal groove, 
rae ot OO with a radula bearing one tooth, with 
1 a distinct digestive gland, and with 
TY, two nephridia opening separately into 
rT a posterior cavity, which also contains 
rt: two gills. The sexes are separate. 
—1-T 
mA Class III. ScaPHOPODA 
a a Very different in many respects from 
7 26. Gasteropoda are the Scaph opoda, of 
ma which Deztalzum (Elephant’s tooth- 
Esl > shell) is the commonest genus. They 
| g are apparently related to the Zeugo- 
me branchiate Gasteropods, and also to 
fo the simplest Bivalves. They burrow 
wa we in the sand at considerable depth off 
wz the coasts of many countries. The 
a w p es mantle has originally two folds, which 
fuse ventrally, and the shell becomes 
cylindrical, like an elephant’s tusk. 
Fic. 231.—Proncomenia, Ner- It is open at both ends. The larger 
vous system.—From Hubrecht. OPEnns (directed downwards in the 
es Coccbeal arigtist sie gout fueueli sand) is anterior, the concave side of 
a'p.g., anterior pedal; ",A.g., pos- the shell is dorsal. The mouth opens 
terior pedal; A.z.g., posterior, vis- at the end of a short buccal tube, 
cerals ; sZ., sublingual connectives; at the base of which is a circle of 
ees ,,cerebro-pedal connective; #e. ciliated tentacles. The foot is long 
ongitudinal pedal nerves ; /a., long- ~. . 2 
ftadinal lateral nerves: with three small terminal lobes. It 
is used in slow creeping, and is pro- 
truded at the anterior opening. There are cerebral and pleural ganglia 
near one another in the head, pedal ganglia in the foot, and a long 
untwisted visceral loop with olfactory ganglia near the posterior anus. 
Sense organs are represented by otocysts beside the pedal ganglia. 
There is an odontophore with a simple radula, The food consists of 
minute animals. There isa much reduced heart, and colourless blood 
circulates in the body cavity. There are two nephridial apertures, one 
