320 Illinois State Laboratory of Natural History. 



D. lobostomata may be easily mistaken at first for D. globu- 

 losa. It is smaller than globulosa, however, and long in 

 proportion to its width. I have, found both species in the 

 stomachs of rotifers. 



15. D. corona Wallich. 



This beautiful and attractive species was moderately com- 

 mon throughout the year, less common in winter, appearing 

 in collections from nearly all of the substations, usually in 

 towings, but often also in shore collections. 



Schewiakoff ('93) identifies this species with D. lobostoma, 

 but in my judgment the two species are distinct. D. corona 

 is larger and more spherical than lobostoma, and the fundus 

 always bears one or more spines. In corona, the border of 

 the mouth has quite a number of lobes or crenulations, while 

 in lobostoma there are usually but three or four lobes present. 

 Among all the specimens of D. lobostoma that I have ex- 

 amined there was but one which had more than three lobes ; 

 and, on the other hand, I have never seen a corona with so 

 small a number of lobes. 



16. D. aculeata Ehebg. 

 Centropyxis aculeata Ehrbg. 



The record of this species shows it to be much scarcer than 

 the two preceding, although occurring pretty uniformly 

 through the year. It was found both in towings and shore 

 collections, and seems to prefer weedy waters. 



17. D. tuberculosa Hempel ('96). 



Found in three out of six towings taken on one occasion in 

 Matanzas Lake in August. But few individuals were found. 

 In the following season a few examples were taken in the 

 river channel at E in September and October. It is easily 

 recognized and remembered by its irregular outline and 

 by the presence of tubercles. 



18. D. fragosa, n. sp. (Fig. 1, 2.) 



This form was found several times, and seems to be new. 



