356 Illinois State Laboratory of Natural History. 



hand, forms like Trochosphara seem to indicate that they are 

 derived from the Annelida. The nervous and excretory sys- 

 tems are very similar to those of the turbellarian worms, 

 which fact seems further to strengthen the theory that the 

 rotifers are related to the Vermes. In the present state of 

 our knowledge it seems best to class them as a separate group 

 under the head of Vermes. 



The entire group has been divided into four well-marked 

 orders, mainly with reference to locomotion. These are the 

 Rhizota, lixed when adult; the Bdelloida, "that swim with 

 their ciliary wreath and creep like a leech;" the Ploirna, 

 " that swim with their ciliary wreath and (in some cases) 

 creep with their toes ;" and the Scirtopocla, "that swim with 

 their ciliary wreath, and skip with arthropodous limbs." 



In the preparation of the following list I have depended 

 largely upon the superb monograph of Hudson and Gosse 

 ('86), from which most of the descriptive matter is taken, 

 and have in the main followed their classification, except in 

 a few cases where it has been shown that they are in error. 

 It seems unnecessary to give the synonymy of any forms de- 

 scribed in the monograph, except perhaps in a few special 

 cases regarding which there are differences of opinion ; -but 

 for all forms in this list that have been described since the 

 publication of Hudson and Gosse's Supplement ('89), a cita- 

 tion is given to the work containing the original description. 



Other rotifers were found, as yet either unidentified or un- 

 described. Owing to limited time and opportunity they were 

 not worked up, and are not included in this list. 



SYNOPSIS OF THE FAMILIES OF ROTIFERA. 



I. Order Rhizota. Fixed when adult, usually inhabiting a 

 gelatinous tube ; foot transversely wrinkled, not re- 

 tractile within the body, ending in an adhesive disc 

 or cup. 

 Flosculariidcs. Coronal cup usually produced into 

 setigerous or ciliate lobes; buccal orifice central; 

 ciliary wreath a single half circle above the buccal 

 orifice; tropin uncinate. (Fig. 3, G.) 



