PLATE VII. 



Fig. 34. Central Nervous System of Tethys cervina Dall and 

 Simpson, in dorsal view. cer. g., cerebral ganglia; 

 ped. g., pedal ganglia ; pi. g., pleural ganglia ; c. p. con., 

 cerebro-pedal connective; c. pi. con., cerebro-pleural 

 connective; pi. par. con., right pleuro-parietal con- 

 nective; pi. v. con., left pleuro-visceral connective; p. 

 com., pedal commissure ; s. c. c., sub-cerebral commis- 

 sure; p. p. com., parapedal commissure. The nerves 

 are numbered serially in the order of their origin from 

 each ganglion. Those of the pleural ganglia are des- 

 ignated pi. i, and pi. 2; those of the cerebral ganglion 

 by the prefix c to their respective numbers, while the 

 nerves of the pedal ganglia are designated by numerals 

 alone, x Anastomosis of a branch of the third cere- 

 bral nerve, c. 3, of the right side with a branch of the 

 second pedal, 2. e., eye. x 18. 



