THE CARNIVOROUS SLUGS OF SOUTH AFRICA. 217 



broadened; end o£ vas deferens swollen to foi-m an epipliallus 

 about 2'5 mm. long, which bears anteriorly a minute flagellum; 

 penial retractor long and narrow. 



Habitat. — Port Shepstone, Natal (Burnup) ; Hilton Road, 

 near Pieterraaritzburg (Biirnup) ; Grahamstown, Cape of 

 Good Hope (Farquhar, French). 



Type. — The type is in the British Museum. Other specimens 

 will be found in the Natal Museum, Pieterniaritzburg, in the 

 South African Museum, Cape Town, and in the Academy of 

 Natural Sciences, Philadelphia. 



Affinities, etc. — This species resembles Apera burnupi 

 in many respects, and was at one time confused with that 

 species. Nevertheless, the two forms can be very easily dis- 

 tinguished by their external charactei's alone, for in the 

 present species the upper keels meet at an acute angle behind, 

 Avhere they form a short median keel, and the lower keels are 

 equally prominent and extend the whole way to the hind end 

 of the animal. The colour of the two forms is also different. 

 Internally the most conspicuous features in which the present 

 species differs from the last are to be found in the pedal 

 gland and the reproductive organs. 



Hitherto this species has usually been known as "Apera 

 burnupi," but an examination of the type-specimen of 

 A. burnupi leaves no doubt that that name should be 

 applied to the preceding species, which Collinge subsequently 

 named A. natalensis, and it has therefore been necessary 

 to give a new name to the present form. 



THE PHYLOGENY OF THE SPECIES OF APERA. 



It is evident that Apera burnupi and A. sexangula 

 are closely related to each other. Of these it is probable that 

 the former is the more highly specialised ; for in the pedal 

 gland, the reproductive organs, and the keels, A. sexangula 

 seems to be rather more primitive than A. burnupi. A wide 

 gap separates these two species from those without keels ; 

 nevertheless, A. purcelli resembles A. burnupi and A, 



