428 O. WESTERN ON DISTYLA SPINIFERA. 



at the junction of the middle and posterior thirds of its length, 

 behind which the surface is deeply excavated. A large bulbous 

 three-jointed foot, which, though retractile, is habitually protruded, 

 emerges through an opening in the posterior part of the ventral 

 shield. Tlie foot ends in two long, narrow, slightly curved, and 

 sharp pointed toes. There is a large single eye placed on a 

 transparent brain. The occipital antenna is large and crowned 

 with a bunch of setse. The trophi of the usual form have four 

 teeth on each uncus. The other internal organs present no 

 peculiarities, and therefore require no separate notice. This 

 Rotifer has to some extent the sleeping habits of the Oathypnadae. 

 I have always found it grubbing about amongst the sandy sedi- 

 ment at the bottom of the pond, and it has a trick of covering 

 itself with small particles of sand, etc., which at times make it 

 difficult to distinguish. Briefly its Specific Characters may be said 

 to be : A facetted lorica higher behind than in front. The dorsal 

 shield, the smaller of the two ; ventral with inverted edges 

 bearing two thorn-like spines on their postero-lateral angles. Foot 

 large, with two long, narrow, curved, and pointed toes. Trophi 

 with four teeth. Size rio". Habitat : Putney Heath. 



Description op Plate XXI. 



Distyla spinifera. 



Fig. 1 . Dorsal view of Rotifer. 

 „ 2. Ventral view. 

 „ 3. Lateral view. 

 „ 4. Trophi slightly crushed. 



