Introduction to Animal Morphology. 289 



There is one doubtful yellow gland in Conus, four in Jan- 

 thina, Littorina, and Dolium, while in Murex the glands of 

 both sides unite to a common duct, and in Umbrella one duct 

 communicates with a large branched organ. In some the 

 saliva contains free sulphuric acid, secreted by a special 

 under lobe, which has a muscular investment.* This part of 

 the gland is tubular ; the rest is acinose. 



A large muscle (columellaris) arises from the lower 

 end of the columella in the body whorl of the shell, 

 and is inserted into the operculum (hence it can shut 

 the shell), into the foot, and mantle edge. In Pulmo- 

 nates, where, as also in Fissurella, it is double and 

 symmetrical, it sends off slips to the tentacles (re- 

 tractorcs tcntacidaruui] and to the buccal mass (re- 

 tractor cs buccales^}. It is crescentic in section in 

 Capulus, and displaced to the right in Haliotis. Its 

 size is generally proportional to the capacity of the 

 shell ; but in Pterotrachea, which has no shell, a cor- 

 responding muscle exists. 



From the upper and hinder wall of the buccal mass passes 

 the pharynx (lined by a reddish epithelium in some Hetero- 

 pods), and the short, longitudinally folded and ciliated 

 oesophagus, which opens sometimes into the middle of the 

 stomach. It has a long glandular diverticulum in Lopho- 

 cercus, or a crop, which may be pear-shaped (Elysia), saccular 

 and unilateral (Tethys, Lymnaea, Planorbis, Buccium), or oval 

 (Dolium, Cypraea, Voluta, &c.) A caecal pouch, filled with 



Dolium Galea, Tritonium nodifcrum, hirsutum, Simpulum corrugatum, 

 Cabcstana cutaceum, Semicassis sulcosa, Cassidaria cchinoplmra, I'hvllo- 

 notus tninculus, Rhinacantha brandaris, Aplysia camclus, I'k-uM>!>: 

 Mcckclii, Pleurobranchus tubcrculatus. In Dolium there is 0.4 per cent. 

 of free H.C1, and 2.7 per cent, of HjSO t . 



t In Opi<-thobraiuhut.i there arc upper and lower pair> of protractors, 

 and one lateral pair of retractors, for the buccal n . ,.tc fmm the 



columellaris. 



U 



