194 Transactions of fhe Royal Society of South Africa. 



teeth on each side, in which both the endocones and the ectocones are split 

 up into a number of small cusps. The relative length of the teeth gradually 

 increases towards the edges of the radula, and the outer marginals are very 

 narrow with scarcely a trace of the ectocones. The transverse rows of 

 teeth curve slightly forwards on each side. The radula of the present 

 species differs from those of 7. {Physopsis africana and other forms chiefly in 

 the relative narrowness of the outer marginal and central teeth, and the extent 

 to which the ectocones of the marginal teeth are split up into separate cusps. 



The salivary glands are very long, narrow, and somewhat convoluted 

 (PI. VIII, fig. 12). They arise directly from the broad buccal mass on each 

 side of the anterior end of the oesophagus, without the interposition of 

 distinct slender ducts. They are broadest a short distance from their 

 front ends ; further back they have a moniliform appearance, being divided 

 by constrictions into a succession of small swellings. The glands pass 

 through the nerve-ring, becoming exceedingly narrow as they do so ; but 

 the greater part of each gland lies in front of the central nervous system. 



The oesophagus is long and rather narrow, with thin walls which usually 

 show longitudinal lines of dark pigment. The anterior division of the 

 stomach is sj^herical, with thick muscular walls, and contains grains of 

 sand. The succeeding thin- walled portion of the stomach is much narrower, 

 and bends downwards on the right, where there open into it together the 

 broad hepatic duct and the so-called j^yloric caecum, a finger-shaped append- 

 age scarcely 2 mm. in length, like that which is found in most Basom- 

 matophora. The intestine curves round the stomach, passing over the 

 oesophagus as it does so, and then describes another loop among the lobes 

 of the liver, before passing forwards as the rectum. The liver lies entirely 

 behind the stomach. 



Chief retractor muscles. — The columellar muscle is broad and powerful ; 

 its central part is inserted in the foot, while its more lateral strands pass 

 forwards to the sides of the head. From its upper surface arise the rather 

 narrow buccal and penial retractors. 



Reproductive organs (PI. VIII, fig. 14). — The reproductive system is of 

 the same general type as that found in the other species of Isidora which 

 have been examined. The hermaphrodite gland is compact, and occupies 

 the apex of the spire posterior to the liver. The hermaphrodite duct is 

 somewhat convoluted, especially in the posterior half of its course, where 

 it is covered with very numerous small vesicular outgrowths. The 

 albumen gland is rather large. The oviduct, which is separate from the 

 male duct throughout its length, is divisible into two parts — a posterior 

 portion which is convoluted and rather narrow and an anterior portion 

 which is more glandular and greatly swollen. An oblique line crosses this 

 anterior portion, the part behind and to the left of the line being trans- 



