THE CAKNiVOKOUS SLUGS OF SOUTH AFEICLV. 155 



and lower tentacles are separated by tlie penis, which projects 

 between them (PI. XIII, figs. 52-57; see p. 190). 



In one specimen of Apera sexangula I found that the 

 retracted upper tentacles were joined by a transverse connec- 

 tion slightly anterior to their junction with the olfactory and 

 optic nerves (PI. XV, fig. 76). The transverse connection 

 was pigmented in the same way as the tentacles themselves. 

 This remarkable abnormality reminds one of the more striking 

 monstrosity figured by Forbes and Hanley/ in which the 

 upper tentacles of a specimen of Agriolimax agrestis 

 {Lin.) were united throughout their entire length. 



The posterior ends of the common tentacular retractors 

 receive nerves arising from the pleural ganglia (or possibly 

 from the short pleuro-pedal connectives) ; and the retractors 

 of the lower tentacles are innervated, as already described, 

 by nerves issuing from the sides of the nerve-collar between 

 the cerebro-pedal and cerebro-pleural connectives, but pro- 

 bably emanating from the cerebral ganglia by the same roots 

 as the nerves to the buccal retractors. 



Beneath the tentacular retractors a few smaller muscles 

 arise on each side and run forward to the anterior part of the 

 head. These are best seen in PI. XIII, fig. 57. The largest 

 of these minor cephalic retractors is inserted in the upper lip 

 of the pedal gland. It is doubtless the contraction of these 

 muscles, together with the combined action of the buccal and 

 tentacular retractors, which causes the front of the head to 

 be invaginated in some specimens. 



THE DIGESTIVE SYSTEM. 



The Mouth and the Eadula-sac. — As in most carnivorous 

 genera, the mouth has three main lips, one dorsal and two 

 lateral, arranged like the sides of an inverted isosceles 



1 ' Hist. Brit. Mollusca,' 1853, vol. i, pi. JJJ, fig. 4. 



VOL. 3, PART 2. 12 



