WATSON : ANATOMY OF HELICAEION. 95 



somewhat qiiiadrate, with concave outer edges ; narrower in the 

 marginal than in the lateral teeth, but rather short in comparison 

 with the length of the cusps. Rows of teeth nearly straight 

 in the admedian area, there being only a very slight angle in 

 the centre, but trending forwards on each side in the region of 

 the marginal teeth. Radular formula : (45 + 9 + 1 + 9 + 45) 

 X 98. 



Alimentary Canal. — Buccal mass large and muscular, the 

 extremity of the radula-sac projecting slightly from its hind 

 end. CEsophagus short, and having, in the specimen examined, 

 a dorsal, backwardly directed pouch at the point where it bends 

 down to pass under the cerebral commissure. Crop nearly twice 

 as broad as the oesophagus, with a projection on the left side at 

 its front end. It passes backwards, without any constriction, into 

 the long and broad, thin-walled stomach. The hind end of the 

 stomach bends down, and from it the intestine passes forwards 

 almost to the heart and then runs back again, describing the usual 

 S-shaped curve, finally passing forwards as the rectum to the anus. 



Salivary Glands rather large, situated above and at the sides 

 of the posterior half of the crop, separate from each other in front 

 but joining above the crop further back. Salivary ducts rather 

 long, issuing from the inner sides of the anterior ends of the glands. 



Liver consisting of a posterior division, which is smaller 

 than usual and occupies the spire beyond the stomach, and an 

 anterior division to the left of the stomach, which is partially 

 divided into three lobes, one lying in each of the two loops of the 

 intestine and one situated chiefly behind the posterior loop, but 

 sending forward a narrow prolongation between the stomach and 

 the rectum. Hepatic ducts opening into the hinder part of the 

 stomach. 



Fre£ Retractor Muscles consisting of four main bands, 

 separate practically from their origin on the columella : the buccal 

 retractor, the right and left tentacular retractors, and a muscle 

 that runs along the right side of the animal just within the body- 

 wall, in which it is inserted near the head. Buccal retractor 

 bifurcating some distance behind the buccal mass, the two divisions 

 being inserted in the right and left sides of its hinder end, and being 

 separately innervated from the corresponding cerebral ganglia. 

 The right division is broader than the left, possibly because it 

 lies in a more direct line between the buccal mass and the columella. 

 Tentacular retractors each dividing further forward than the 

 bifurcation of the buccal retractor into a large muscle inserted 

 in the upper tentacle and a smaller one inserted in the lower 

 tentacle on the same side. Retractor of the right upper tentacle 

 passing between the penis and the vagina. Penial retractor very 

 short, passing from the front of the diaphragm to the posterior 

 end of the penis. No free pedal retractors occur in the body-cavity. 



