362 Illinois State Laboratory of Natural History. 



sphere into two hemispheres, and passing ahove the buccal 

 orifice ; dorsal gap in the wreath at the pole opposite to 

 buccal orifice; secondary wreath a fragment on the under 

 side of the buccal orifice ; ventral antennae extremely minute ; 

 no tube. 



8. T. solstitialis Thorpe. 



The occurrence of this rare and remarkable form in this 

 country was reported for the first time by Dr. C. A Kofoid 

 ('96a). It was found by him in the Illinois River and Flag 

 Lake in June, July, and August, 1896. 



CONOCHILUS EHRBG. 



Clusters of several or many individuals, free-swimming; 

 corona horse-shoe shaped ; gap in the ciliary wreath ventral. 



9. C. dossuarius Hudson. 



This species was found in all the bodies of water under 

 observation. It was present during the greater part of the 

 year from January to September, reaching its maximum in 

 March. Many clusters were taken with a tow-net in Thomp- 

 son's Lake, in February, 1895, under eighteen inches of ice. 

 These specimens appeared larger and more vigorous than 

 those seen during the summer. It is readily recognized by 

 the small number of individuals composing the cluster; by 

 the presence of the two antennae, which stand out on the 

 arched ventral surface like tall chimneys on a building ; and 

 by the fact that eggs are almost invariably found in connec- 

 tion with the colonies. 



10. C. unicornis Rousselet ('92). 

 C. leptopus Forbes, '93. 



This rotifer was found only in May and June. During this 

 time only a few were taken in the tow-net at C, although it 

 was common in the river at D and E, and was taken in both 

 surface and oblique towings at the latter substation. 



Order BDELLOIDA. 



Family PHIL.ODINID.ffi. 

 Rotifer Schrank. 



Eyes two, situated within the frontal column. (Tropin, 

 Fig. 3, 4.) 



