312 Illinois State Lahoratory of Natm^al History. 



The posterior part is slightly excavated on the dorsal 

 and ventral surfaces around the foot, the ventral exca- 

 vation being more pronounced than the dorsal. The pec- 

 toral edge is slightly indented in the center, the edges 

 sloping uniformly from the lateral edges to the middle. 

 A small red eye is situated just in front of the large 

 mastax. A dorsal antenna is prominent in the sinus 

 between the antlers. The foot is long and wholly re- 

 tractile. The eggs are carried about fastened to the 

 posterior part of the lorica. 



The characteristic features of this rotifer are the shape 

 of the lorica, the latero-posterior inangulations, the shape 

 of the occipital spines, and the small spines covering the 

 surface of the lorica. Its nearest ally is B. hudapedi- 

 nensis Daday (Plate XXIII., Fig. 6), from which it differs 

 in the form of the lorica, in the size and shape of the 

 occipital spines, and in the shape of the foot orifice. 



This is a lively little species, and is found only in clear 

 water, away from vegetation. Length of lorica, includ- 

 ing sjiines, .151 mm. to .172 mm.; width .092 mm. to 

 .out) mm. 



Biachionus mollis n. sp. 



(Plate XXIV.. Fig. 7 and 8.) 



Lorica thin, smooth, oval in outline; the dorsal 

 surface highly arched; ventral surface but slightly 

 convex. The anterior margin straight and truncated. 

 No occipital or posterior spines. A very prominent dor- 

 sal antenna near the anterior maigiii. 



This species is peculiar in having a very thin, soft 

 lorica and no spines. When the animal contracts, it 

 frequently invaginates those parts of the lorica that 

 serve as attachments for the muscles. The foot ori- 

 fice is guarded by a collar. The foot is very large 

 and long, is wholly retractile, and ends in two small 

 toes. The toes ai'e very characteristic for this species. 

 Viewed either dorsally or laterally, they taper to 



