MORPHOLOGY OF THE HELICINIDiE. 769 



anterior part of the broad raclular ribbon. The median and 

 admedian radular teeth lie in the floor of this trough, the great 

 lateral teeth lie in the angles between its floor and sides, and 

 the uncini form curved rows running upwards and backwards 

 along its sloping sides. The radular ribbon is attached by strong- 

 muscular bands to the cartilages. These muscles run obliquely 

 forwards from the radula to be attached to the anterior cai'tilage 

 of either side, and obliquely backwards to be attached to the 

 posterior cartilages, these two sets of muscles causing the ribbon 

 to slide forward and backward over the smooth surfaces of the 

 ca,rtilages. 



The relation of the oesophagus to the radular sac and odonto- 

 phore is shown in fig. 3, which is a drawing of a dissection of 

 these structures in Alcadia palliata. The left oesophageal pouch 

 and the left side of the oesophagus have been cut away, and the 

 roof of the oesophagus has been lifted back to the right side to 

 show the entrance to the right oesophageal pouch and other 

 structures. In the angle of the deep fold between the oesophagus 

 and radular sac are seen the buccal ganglia (g.bicc.) lying just above 

 the middle of the anterior odontophoral cartilages. The opening 

 of the oesophagus into the pharynx, situated just in front of and 

 above the buccal ganglia, is irregularly funnel-shaped, with thick- 

 ened and folded lips projecting forward into the pharyngeal 

 cavity. Laterally, these lips are deeply grooved, and on either 

 side the groove is continued backward and downward into the 

 lateral pharyngeal diverticulum described above, and upward and 

 somewhat forward into the anterior salivary gland of its own 

 side. These anterior salivary glands are formed by a pair of pocket- 

 like forward projections of the oesophagus, which in their natural 

 position lie side by side and form a pair of pouches lying above 

 the cerebi^al commissure. Between them is an anterior ctecal 

 diverticulum continuous behind with the median dorsal groove of 

 the anterior part of the oesophagus. When separated by an 

 incision in the mid-dorsal line and turned outwards, the anterior 

 salivary glands present the appearance shown in fig. 2. Inter- 

 nally their walls are raised into a number of thick glandular 

 ridges : the outermost of these ridges is specially thick and is 

 continued downward, in the groove passing to the side of the 

 oesophageal orifice, into the glandular ridge on the outer wall of 

 the phaiyngeal diverticulum, as has been described above. 



The anterior section of the oesophagus, lying above the 

 odontophore, is fairly wide. Internally, its walls present a 

 number of longitudinal glandular ridges, and in the mid-dorsal 

 line there is a deep groove bounded internally by prominent 

 ridges ; posteriorly this groove shallows and eventually dies out. 

 On either side of this anterior section of the oesophagus is a 

 gaping oval orifice (figs. 2 & 3, o.ce.p.) leading into the large 

 oesophageal pouches, or, as some would call them, the posterior 

 salivary glands. The last-named structures are capacious irregu- 

 larly lobulated sacs with large cavities. Their inner walls are 



