164 TWELFTH ANNUAL REPOKT. 



Body flattened or sub-cylindrical. Abdomen usually not much 

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

 constriction; antennae rather short, 4- to 10-jointed; mandibles 

 strongly toothed, palpate; maxillae well developed, palpate; first 

 pairofoiaxillipedes 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.e, 



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

 other sub-families of Harpacticidas by the fact that the seconp 

 maxilliped has a prehensile hook. The feet of first pair are not 

 clawed, but have the inner branch elongated, and the palp of the 

 mandible is one-branched. 



Genus Canthooamptus, 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 Cantliocampti congregate 

 on the exposed side. 



Canthocamptus 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 segment 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 cray-fish. Above 

 the beak, in the center of the forehead, is the eye, consisting of 

 pigment and two lenses, showing that we really have to do with 

 two eyes confluent 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 



