BDELLOID ROTIFERA OF SOUTH AFRICA. 181 



when the slide is examined at any time, it will be found either 

 feeding freely, or completely contracted into a ball — less seldom 

 will it be found creeping. It sometimes lies for so long a time- 

 contracted that one has difficulty in deciding whether it is alive 

 or not. I once put one aside as dead, and on again examining 

 the slide in which it was, for some other purpose, found it feed- 

 ing briskly. 



Its shape varies very little on account of the extremely thick 

 skin. There is never a wrinkle in the trunk, only, when it sits, 

 back feeding, the trunk widens out, but the shape is perfects 

 It has a habit when feeding of pushing forward the first trunk 

 segment towards the antenna, till it stands out like a frill. 



The rump is the most distinctive part. It is not particularly^ 

 heavy, and rises up — fairly flat across — for a considerable dis- 

 tance backwards, then dips sharply down forming an elbow 

 ridge, which is practically rigid owing to the stiffened material 

 bounding it. I have never seen the ridge obliterated, even 

 when the foot is fully extended. Fig. 236 gives a side view. 



The corona is large and graceful, and the wide sulcus equal 

 to three-fourths of the wheel-width. Corona, collar and neck 

 are to each other as 37, 22 and 18. There is a comb-like ridge 

 which runs across the wheel, and extends well into the sulcus 

 with a bold curve. The central part of the upper lip front 

 margin (fig. 23a) is copied from the few samples lately seen, 

 and is rounded ; but in all the large number of specimens ex- 

 amined formerly, the central part is distinctly triangular with 

 a sharp apex. The Grahamstown examples were rather smaller 

 in size than the Umtata ones. 



The dental bulb is extremely large — about 1 /500th inch — 

 and is surrounded by a heavy muscular mass. Two teeth are 

 very broad, and two, one on each side of these, are smaller, 

 about one-fourth the size of the others, but occasionally one of 

 these is wanting or scarcely noticeable. There is a large granular 

 gland behind the bulb. 



The intestine is large and heart-shaped, and very thick 

 walled. There is a distinct, narrow, button-like muscular cinc- 

 ture between the intestine and the stomach (fig. 23). 



The spurs, on the first segment of the foot, are blunt and 

 flat, and lie near each other. 



The stippling is of the same nature as that of Philodina grandis^ 



