492 Mr. Garner on the Nervous System of Molluscous Animals. 
* 
filaments, one to complete the ring (5.), on the lower part of which two 
separate locomotive ganglia (B.) are formed ; and two others on each side, one 
(f.) of which attains the visceral organs, meeting the filaments from the pha- 
ryngeal ganglia, and not,in this case forming a visceral ganglion or plexus, 
the other pair being the nerves of the mantle (0.) and muscular cavity in which 
the branchize are found. "The right one of these last crosses over the ceso- 
phagus, and forms a ganglion (H.) in the left side, the left one here not 
crossing under the digestive canal, as, however, it often does: the direction 
being reversed in sinistral shells. In the first case the right branchial appen- 
dage has mounted over the body of the animal, and is the one most de- 
veloped ; the corresponding nerve having accompanied it, and been developed 
into a ganglion. "This is not the posterior ganglion of bivalves, that having 
become incorporated in the lateral ganglia of the brain. 
In Paludina (fig. 6.) we see better the two lateral ganglia (A.) to be com- 
posed each of two others, and each portion is united to the pedal ganglion (B.) 
by a separate chord, the posterior chord being shown by-analogy to be the 
nerve connecting the two ganglia, which are united to the cerebral, in consent 
with each other. The right is largest, giving nerves to the penis (r.) from near 
the optic. "These ganglia supply as usual the eyes, tentacles and mouth ; the 
pedal gives nerves to the foot (d.) and shell-muscles (e.). Two large nerves 
(c.) go from the superior ganglia to supply the mantle, branchiz, viscera, and 
in part the shell-muscles. 
In Turbo (fig. 8. we have also the two sentient ganglia (A.) at a distance 
from each other, each composed of two others sending down two twigs (b.) 
to the pedal ganglion (B.). From the anterior part of the lateral ganglia 
the nerves of the eyes and tentacles (g.) and mouth are as usual derived. 
From the posterior part we have the branchio-visceral nerves, forming a 
small ganglion at the back of the branchial sac of the animal supplying the 
branchiz and viscera, —and two external respiratory nerves (0.), each form- 
ing a ganglion (H.) in the flank, supplying the mantle, and in part the - 
branchiz, also the shell-muscles, as well as the lateral appendages, often de- 
. veloped in this genus. There are also a few filaments (p.) to the floor of the 
branchial sac and side of the animal. With the pharyngeal ganglia (D.), 
which it is needless any further to describe from their uniformity, there are 
