bloomer : anatomy of ceratisolen and solecurtus. 39 



Nervous System. 



The cerebro-pleural ganglia are situated between the posterior 

 portion of the anterior adductor muscle and the ventral integument, just 

 anterio-laterally to the retractor pedis anterior muscles. They lie some 

 distance apart, and are joined by a commissure. Anteriorly, each ganglion 

 gives rise to a nerve, which passes underneath the anterior adductor 

 muscle, innervating it, and then continues as the pallial nerve. 



Posteriorly, a connective joins each cerebro-pleural with the viscero- 

 parietal ganglion. The connective passing between the retractor pedis 

 anterior muscle and the body wall, buries itself in the latter, shortly after- 

 wards it emerges and clings close to the wall. Then, becoming free, it 

 continues between same and the viscera until it reaches the bifurcated 

 parts of the retractor pedis posterior muscles, and passing through the 

 inside wall, joins the viscero-parietal gangHon. 



Each cerebro-pleural ganglion is also joined by a connective with the 

 pedal ganglion. The connective immediately becomes buried in the 

 muscular body wall ; and passing between the longitudinal and trans- 

 verse muscles of the foot, joins the pedal ganglia. 



The viscero-parietal ganglia are large, and situated between the bifur- 

 cated portions of the retractor pedis posterior muscle. Posteriorly the 

 ganglia give rise to two branchial nerves, which pass directly to the gills ; 

 also to two nerves, which give of! a number of branches, innervating 

 the posterior adductor muscle, the posterior portion of the dorsal integu- 

 ment, and the siphon. On each side one large branch — the pallial nerve — 

 crosses the siphonal retractor muscle, and continues round the mantle 

 lobe as the circumpallial nerve. 



The pedal ganglia are situated in the proximal portion of the foot above 

 about the centre of the caecum of the crjstalline style, among the transverse 

 muscles, and are surrounded by muscular connective tissue. They give 

 of? a number of nerves, which, passing between the longitudinal and 

 transverse muscles, innervate the foot. 



Soleeuptus eandidus. 

 External Characters. 



The anterior portions of the mantle lobes curve slightly more than 

 in /5'. strigillatus. Posteriorly the lobes from a more anterior position 

 over the posterior adductor muscle take a greater curve, and 

 consequently project more posteriorly. The edges of the lobes are more 

 crenulated, particularly the parts bordering the pedal cavity, and they 

 carry a tentacular fringe. The edges of the mantle lobes are of an orange 

 colour, while the remaining part of the animal is nearly white, with the 

 exception of the distal portion of the foot, which has a dirty orange tinge. 

 The internal structure is similar to S. strigillatus. It is impossible to say 

 whether the slight difterences noticeable are constant or not, owing to the 

 limited number of specimens examined. 



