BDELLOID ROTII'EilA OF SOUTH AFRICA. 165 



wanted for comparison. Afterwards it became quite an easy- 

 matter to distinguish between the two, creeping or feeding. 



H. elusa generally feeds with its head above the horizontal, 

 and the tip of the upper lip is not then seen projecting at the 

 front, but lies over the narrow sulcus, which usually shows a 

 black space owing to interference, when practically no details can 

 be made out. When the head is exactly on a level with the body 

 the peculiar nature of the upper lip may be seen, but as a rule 

 it requires much patience and needs much searching before one 

 is observed feeding at the right angle. The lip is fairly broad in 

 front with a small notch in the middle. Laterally there is a fold, 

 from the top corner to some distance down, turned in over but 

 not quite down on to the rest of the upper lip, leaving a space 

 below running into the corner. 



The rump is very distinctive, with the triple folds of skin on 

 each side. The middle one is the largest and recalls H. crenata, 

 but the prominence in the latter does not seem to be a wide fold 

 of the skin — from the description — and is stated to be clear of 

 stippling, whereas the folds in H. elusa are heavily stippled like 

 the rest of the rump. 



The first segment of the foot is sufficient to distinguish H, 

 elusa from other species. 



I do not think I have ever seen H. crenata, but there is evidently 

 a resemblance in its general outline to that of H. elusa. The 

 different type of upper lip, however, is alone enough to show that 

 the two are distinct species. 



H. elusa differs in many points from the description of H, 

 crenata by Murray. 



The corona of the former is proportionately much wider, and 

 the front margin of the upper lip is quite different, having a 

 notch. 



It has a decided colour, whereas H. crenata is colourless. 



It never has a crenate appearance, and the stippling is most 

 pronounced on the first segment of the foot, while in H. crenata 

 it diminishes on the foot. 



The rump has three folds of thick skin and all stippled. In 

 H. crenata there is but one round prominence, which is stated 

 to be free of stippling. H. elusa has no boss on the foot and its 

 spurs have a straight interspace. The inclosed discs are large. 

 The egg is not narrowed at the anterior end. H. elusa is not 



