492 Mr. Garner on the Nervous System of Molluscous Animals. 



filaments, one to complete the ring (i.), on the lovt^er part of which two 

 separate locomotive ganglia (B.) are formed ; and two others on each side, one 

 {/.) 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 (o.) and muscular cavity in which 

 the branchiae are found. The right one of these last crosses over the oeso- 

 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 Paludhia (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 lai'ge nerves 

 (c.) go from the superior ganglia to supply the mantle, branchiae, viscera, and 

 in part the shell-muscles. 



In Turbo (fig. 8.) we have ab>o 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 

 branchiae and viscera, — and two external respiratory nerves (p.), each form- 

 ing a ganglion (H.) in the flank, supplying the mantle, and in part the 

 branchiae, 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 



