BDELLOID ROTIFERA OF SOUTH AFRICA. ] 53 



The rostrum is long and stout, and seems to have the quadruple 

 lamella, but of this I could not make quite sure. There is a large 

 brain mass. The dental bulb is winged and has two strong teeth. 



The trunk is almost equal to the rest of the animal in length 

 and shows five clear divisions of about equal length. It has the 

 toughness and elasticity of skin of M. musculosa, which enables 

 it to keep a perfectly regular shape, whether extended or con- 

 tracted. 



The lumbar region has what might be called the " crinoline " 

 type. The anal segment stands out with a sort of thin almost 

 rigid flange at bottom — one could almost imagine a wire support 

 inside — so that whatever tightening or alteration takes place in 

 front, the posterior maintains its wide and peculiar shape. The 

 pre-anal segment also keeps its shape as if it were stiffened. 

 Whether the animal is stretched or relaxed, the shape of the 

 rump is practically constant. The lumbar region, seen sideways, 

 looks the deepest part of the body, largely due to the lumbar 

 plicae standing up so high. These lumbar plicae, which look like 

 two firm smooth membranes with their lower edges deep down, 

 rise up above the surrounding surface ; the upper edges have a 

 convex curve longitudinally. There is an abrupt dip from the 

 anal segment to the foot. The intestine is a large oval, but the 

 contractile vesicle is rather small. 



The foot has four segments, and has no boss. Of the segments, 

 the first is the longest and ends in a rigid rim, the second has also 

 a rim but smaller. The spurs are divergent and decurved, and 

 as long as the width of the ankle. There is a very short inter- 

 space, and a slight shoulder is usually apparent just below. The 

 spurs are often clipped together. 



The corona is bold, and is to the collar as 14 to almost 11. The 

 upper lip is clear cut and of a glassy colour. It rather more 

 than covers the sulcus, and has a clean-cut almost straight 

 front margin. About half-way back there is a line or ridge 

 across the lip, and between this and the front margin on the 

 lateral borders are two curves, probably defining skin folds. 

 There is a short fleshy tooth on the sulcus bridge w^hich shows 

 in certain positions only, when the head is well up. 



The egg is a broad oval, almost round, and has blunted narrow 

 prominences all over the surface, almost touching each other, 



M, timida can be kept in a slide for a considerable time. 



