Fio. 123. 



Nervous system of 3 Streptoneurous Gastropods, showing the dialyneury and zygoneury, 

 dorsal aspect. A, Paludina (after Bouvier, somewhat modified); B, Triton (after Haller); C, 

 Lamettaria (after Bouvier). ab.</, abdominal ganglion ; Ir.n, branchial nerve ; ce.g, cerebral 

 ganglion ; c.pe, cerebro-pedal connective ; c.pl, cerebro-pleural connective ; tli', di", left and 

 right dialyneury ; i.i.g, infra-intestinal ganglion ; ot, otocyst ; pa.n, pallial 7ierve ; ye.g, pedal 

 ganglion ; pl.g, pleural ganglion ; pl.pe, pleuro-pedal connective ; s.i.g, supra-intestinal ganglion ; 

 st.g, stomato-gastric ganglion ; vi.c, visceral commissure ; vi.cf, vi.d', supra-intestinal and infra- 

 intestinal part of the visceral commissure ; zjA zy", left and right zygoneury. 



143 



