ENTOMOSTRACA OF MINNESOTA. 125 



The general form and structure closely resembles that of the Gyclopidce. 

 The following characters are the more important ones in distinguish- 

 ing the family from the other families of the order: 



Body flattened or sub-cylindrical. Abdomen usually not much 

 smaller than the thorax, from which it is not separated by a sudden 

 constriction; antennse rather short, 4- to 10-jointed; mandibles strongly 

 toothed, palpate; maxilhce well developed, palpate; first pair of maxil- 

 lipeds with strong teeth at the end, second pair usually forming a 

 claw. The first pair of feet are often turned forward or prehensile; 

 fifth pair one- or two jointed, serving as egg supports in the female. 



Most species live among sub aquatic vegetation. 



THE SUB-FAMILY CANTHOCAMPTIN^, 



To which our sole genus belongs, is further distinguished from the 

 other subfamilies oi Ilarpacticidw by the fact that the second maxilli- 

 ped has a prehensile hook. The feet of the first pair are not clawed, 

 but have the inner branch elongated, and the palp of the mandible is 

 one-branched. 



GENUS CANTHOCAMPTUS Westwood. 



These little animals may be secured in considerable numbers by 

 gathering a supply of water from among weeds in shallow ponds and 

 permitting the debris to settle in a spot where light only touches the 

 jar from one side, when the Canthocampti congregate on the exposed 

 side. 



Ckinthoeamptus is an elongated animal, with the body divided rather 

 obscurely into two portions, of which the first, or anterior portion, is 

 largest. This part of the body has five segments, each of which has 

 at least one pair of appendages. The first, consisting of the head 

 proper with one of the somites of the body or thorax, as is discovered 

 by observing that a pair of legs is attached to it, is the largest seg- 

 ment of the body. 



As seen from above, it is triangular and extends in front into a 

 short, stout beak or snout, like the rostrum of a crayfish. Above the 

 beak, in the centre of the forehead, is the eye, consisting of pigment 

 and two lenses, showing that we really have to do with two eyes con- 

 fluent on the median line. This is the simplest form of a compound 

 eye. The same method of compounding the eyes is exhibited in a 

 more complicated manner by Daphnia and other Cladocera. On either 

 side of the beak springs an antenna with six to nine joints of unequal 

 size. The first three joints are profusely covered with hairs. The 

 fourth joint is more slender than the preceding, and terminates 

 in a process below, which bears besides a long hair a peculiar blunt 



