246 MA.RTIN F. WOODWARD. 



fairly large nerves (figs. 21, 22, 28, 29) ; one of these runs 

 forwards between the cerebro-pleural and cerebro-pedal con- 

 nectives (fig. 22) to the muscles of the side of the neck, 

 while the other runs up to the body-wall above the crop to 

 the floor of the mantle cavity; this last may be Bouvier and 

 Fischer's pallial nerve, although it does not arise at the same 

 spot. I do not feel at all certain about the identity of these 

 nerves, since I have not been able to trace any of them to 

 the free mantle-fold, and consequently am not inclined to call 

 any of them pallial nerves. Still less am I satisfied concern- 

 ing the presence of the primary pallial nerves of these 

 authors, and I take it that they rather assume that such 

 nerves must be present. An examination of their fig. C, op. 

 cit., p. 170, will show two large nerves arising from the upper 

 part of the pleuro-pedal cords, the anterior of these corre- 

 sponding with the nerve marked with an asterisk in my figs. 

 21 and 22 ; the nerve runs up parallel to my pleuro-pedal 

 connective, branching repeatedly, and is eventually lost in 

 the muscle of this portion of the body : it is possible that 

 some of its finer fibres may penetrate into the mantle. With 

 regard to the second, which they represent as co-extensive 

 with the pleuro-pedal cords, I can only say that it does not 

 exist in P. Beyrichii. Behind the last-mentioned nerve a 

 series of four small nerves are seen to arise from the pleural 

 poi'tion of the pleuro-pedal cords, between the point of origin 

 of the first and second pedal nerves (figs. 21 and 22, p.^ and 

 p.'^). These nerves, which are distributed to the muscles on 

 the dorsal surface of the foot where the latter joins the body, 

 — i. e. to the commencement of the columella muscle (fig. 28) 

 — are the only nerves which occur in the region corre- 

 sponding to that whence Bouvier and Fischer's great hypo- 

 thetical pallial nerve springs ; they are, however, quite small, 

 and I have not been able to trace them beyond the columella 

 muscle. Since I cannot think that there is likely to be any 

 great difference between the different species of Pleuroto- 

 maria in this respect, I can only conclude that the great 

 primary pallial nerve of Bouvier and Fischer does not exist 



