OF NORTH AMERICA. 513 



glion of right side; 4, abdominal ganglion; 5, visceral ganglion of left side; 

 6, pleural ganglion of left side; 7, pedal ganglia (separated and pulled away 

 from their natural position); 8, buccal ganglia; 9, superior frontal nerve 

 to labial region; 10, eye; 11, optic nerve; 12, nerve to right tentacle; 13, nerve 

 to the neck ; 14, nerve to penis-sac ; 15, nerve to head of penis ; 16, inferior cervi- 

 cal nerve of right side; 17, large labial nerve; 18, superior cervical nerve; 19, 

 inferior cervical nerve to left side; 20, lateral mantle nerve; 21, anterior mantle 

 nerve; 22, aortic nerve; 23, sub-intestinal nerve; 24, right pallial nerve; 25, 

 osphradium or organ of 'Smell ; 26, left, 27, right columellar nerve ; 28, superior 

 pedal nerve; 29, central pedal nerve; 30, inferior pedal nerve; 31, otocyst or 

 auditory vesicle; 32, nerve to labial arteries; 33, anterior pellial nerve. 



PLATE VI. 



Figure A. Superior and lateral jaws of Lymnaa stagnalis appressa SAY. 1, 

 superior jaw; 2, 2, right and left lateral jaws. 



B. Superior jaw of Lymncea stagnalis sanct&marice WALKER. 



C. Superior jaw of Pseudosuccinea columella (SAY). 



D. Superior jaw of Radix auricularia (LINNE). 



E. Superior jaw of Bulimnea megasoma (SAY). 



F. Superior jaw of Galba obrussa (SAY). 



G. Superior jaw of Galba cubensis (PFR.). 



H. Superior jaw of Galba umbilicata (ADAMS). 



I. Superior jaw of Galba palustris (MULLER). 



J. Superior jaw of Galba emarginata (SAY). 



K. Superior jaw of Galba catasc opium (SAY). 



L. Superior jaw of Galba caperata (SAY). 



M. Superior jaw of Galba catascopium (SAY). Worn. 



N. Radula of Galba doddsi BAKER. 1, first lateral; 5, 7, 8, inter- 

 mediate teeth ; 9, 10, typical marginal teeth. 



O. Galba obrussa plica (LEA). Intermediate or seventh tooth of the 

 radula. 



P. Radula of Galba hendersoni (BAKER). 9, intermediate tooth; 10, 11, 

 lateral teeth. 



PLATE VII. 



RADULA. 



Figure A. Lymncea stagnalis appressa SAY. C, central tooth ; 1, 2, lateral teeth ; 

 16, 19, lateral teeth with a second cusp above the ectocone; 

 20, 21, intermediate teeth; 23, 32, 34, marginal teeth; 38, 44, 

 outer marginal teeth. 



B. Pseudosuccinea columella (SAY). C, central tooth; 1, first lateral; 



11, first intermediate; 13, 14, 15, 18, typical marginals; 27, 30, 

 outer marginals. 



C. Radix auricularia (LINNE). C, central tooth; 1, first lateral (tri- 



cuspid) ; 2, 9, lateral teeth (bicuspid) ; 10, 11, 13, intermediate 

 teeth; 15, 20, typical marginal teeth. 



D. Bulimnea megasoma (SAY). C, central tooth; 1, first lateral; 2, sec- 



ond lateral; 6, modified lateral; 14, outer lateral; 17, intermedi- 

 ate tooth; 18, 19, 21, marginal teeth. 



