416 Illinois State Lctboratory of Natural History. 



them are scavengers, though some species feed upon min- 

 ute aquatic vegetation, such as diatoms and filamentous 

 Algae. 



Ten of the species and both of the families herein 

 treated were represented in collections of the Biological 

 Station from the region covered by its operations in the 

 vicinity of Havana. The collections examined were partly 

 surface, bottom, and oblique tows taken with a fine tow- 

 ing net in the deeper and more open waters, and partly 

 catches with the towing net or Birge net from among 

 the vegetation along the gently-sloping shores. 



In the first table following, the distribution of each 

 species is shown with regard to the various collecting sub- 

 stations, which are grouped according to their general 

 character. Full descriptions of these localities may be 

 found in a previous article of this volume.* The total 

 number of collections examined from each substation is 

 given immediately beneath the letter designating the sub- 

 station. The lower, larger number of each pair in the 

 table indicates the relative abundance of the species, on 

 the scale of 5, 1 meaning rare, and 5, excessively 

 abundant. The smaller numbers above these show the 

 number of collections in which the species appeared. 



It will be seen that in the off-shore collections the fii'st 

 three genera (Limuicythere, Cyprinotus, and Candona) 

 do not appear at all, while the last two (Cypria and 

 Cypridopsis) appear a number of times. This indicates 

 a difference in habits, and does in fact correspond to 

 a decided difference in structure. The members of the 

 second group possess well-developed swimming hairs or 

 natatory setae, and appear not only in the bottom tows 

 but in the surface tows also, even in the river channel 

 at station E. 



• Article VI.. p. 151. 



