378 Illinois State Lahoratori/ of Natural History. 



transversely wrinkled, jointless, toeless, ending in a ciliated 

 cup. 



82. P. patina Ehrbg. 



This species was present throughout the entire year, and 

 was found in the river and in all the deeper lakes. As to 

 the shallower lakes, it was rare in Flag and not found at all 

 in Phelps. It occurred both in towings and among vegeta- 

 tion. Its period of abundance is evidently from June to 

 October. 



83. P. valvata Hudson. 



Very rare, being found only once — among vegetation in 

 Quiver Lake, in June, 1894. 



Family BRACHIONIDiE. 



Brachionus Ehrlg. 



Lorica without elevated ridges, gibbous both dorsally and 

 ventrally ; foot very flexible, uniformly wrinkled, without 

 articulation ; toes very small. 



84. B. mollis Hempel ('96). 



This active species was found, during July and August, in 

 towings from the Illinois River, Phelps Lake, and Flag Lake, 

 but was not common except in Phelps Lake, where it was 

 abundant. 



85. B. pala Ehrbg. 



This species was present all the year round, and was found 

 at nearly all of the substations. It was very abundant at 

 times, especially in April, August, September, November, 

 and December. 



There seem to be several varieties of this species. Some 

 individuals have no posterior spines ; others have the two 

 prominences which guard the foot developed into spines, and 

 also have two other posterior spines. There are still others 

 in whi(-h tliese posterior spines are remarkably developed, so 

 that they are twice the length of the occipital spines. 



This is undoubtedly a pelagic species, since it was found 

 in surface and bottom towings, and but once among vegeta- 

 tion near the shore. 



