176 Transactions of the Royal Society of South Africa. 



and outer lip normal there is often no trace of rimation, while the columella 

 is frequently clearly truncate. 



External features of animal. — The foot-sole is undivided. The foot- 

 fringe is rather broad, crossed by transverse grooves, and limited above 

 by a conspicuous peripodial groove on each side. Posteriorly the peri- 

 podial grooves curve together and unite over a caudal mucous pore, as shown 

 in PL VII, fig. 2, which also shows the rounded, almost truncated, form of the 

 posterior extremity of the foot. There is no keel. An oblique lateral groove 

 runs forward on each side of the neck. The dorsal grooves are incon- 

 spicuous and rather close together ; in front they branch into four or five 

 well-marked vertical grooves on the front of the head. The labial palps 

 are well developed, and the generative opening is situated rather far back 

 on the right side of the head (PI. VII, fig. 7). 



The ground-colour of the skin is light red or salmon, this being the 

 tint of the dermal grooves. Between the grooves, however, the rugae are 

 more or less tinged with dark grey pigment. This dark pigment is most 

 developed on the sides of the animal, leaving a paler dorsal area. On the 

 neck this median dorsal area is lightest towards the edges, which are well- 

 defined and contrast strongly with the dark lateral zones. The entire foot- 

 sole is slightly tinged with the dark grey pigment. 



The thin skin of the mantle and visceral hump is largely translucent 

 and colourless, but it is ornamented over the lung, etc., with some vertical 

 or oblique, irregular, brownish grey lines, which are darkest towards the 

 suture, the broadest line being near the respiratory opening ; and there 

 are also some vertical, irregular, opaque white streaks over the exposed 

 parts of the liver, stomach, etc. (PL VII, fig. 6). These white streaks are 

 most defined and relatively largest towards the apex ; and both they and 

 the dark lines on the last whorl show clearly through the translucent 

 brown shell.* 



The mantle-edge is whitish, and is provided with the usual right and 

 left body-lobes, the latter being divided into two widely separated portions, 

 one near the respiratory opening, and the other on the left side of the 

 animal. 



Pallial organs. — The main pulmonary vein is without important 

 branches, the roof of the lung only showing this single vessel passing for- 

 wards. The kidney is long, being about half the length of the lung and 

 extending a considerable distance in front of the heart, as in Ps. hoivini. 

 The ureter arises from the extreme front end of the kidney, and runs back 

 along its upper edge to the hind end of the lung ; it then curves round and 

 runs forward immediately beneath the rectum (PL VII, fig. 6). 



Central nervous system. — In the specimen examined the cerebral 



* Another specimen had more numerous dark lines and .spots than the one figured. 



