THE CRUSTACEA OF NEW JERSEY. 8i 



with iDair of swimming'-feet, consisting typically of two- jointed 

 base and two like three-jointed rami. The symmetry frequently 

 broken by retardation of development of inner ramus, while fifth 

 pair of feet may become rudimentary and in various ways sub- 

 serve organs of sex. Five abdominal segments nearly devoid of 

 appendages and continued posteriorly by two caudal stylets which 

 bear strong setae constituting, in many forms, a tail-fin or spring-. 



These minute and mostly predaceous animals are not only use- 

 ful as scavengers but supply the food of most fish fry, as well 

 as of other animals. They are distributed in both salt and fresh 

 water, and while the latter forms are perhaps few in species 

 they make up in the numerous individuals. 



Though the scheme of divisions into suborders as adopted by 

 Giesbrecht is used here, very likely the more recent vieM^s of G. 

 O. Sars, who admits seven, as the Lernseoida, Caligoida, Mon- 

 strilloida, Notodelphyoida, Cyclopoida, Harpacticcida and Calan- 

 oida, will be found necessary. 



Key to the sub-orders. 



a. Free-swimming, or ectoparasitic ; body mostly elongated ; eggs de- 

 veloped in brood-pouches attached to base of abdomen. EucopEpoda 

 aa. Ectoparasitic ; whole body strongly depressed, broad ; eggs not developed 

 in brood-pouches. branchiura 



Sub-Order EUCOPEPODA. 



Free-swimming or ectoparasitic animals. Swimming-feet bi- 

 ramous. Biting-jaws developed, or when parasitic degenerate 

 and jaw^s often adapted for sucking. Eggs developed in brood- 

 pouches attached to base of abdomen. 



Key to the tribes. 



a. Mouth not furnished with organs adapted to mastication, but with an 

 apparatus fitted for sucking; feet partly formed for walking or pre- 

 hension, partly branchiferous and fitted for swimming ; body usually en- 

 closed in buckler of one or two pieces ; parasitic. gymnoplea 

 aa. Mouth furnished with organs adapted to mastication ; feet mostly adapted 

 for swimming; body enclosed in buckler, articulations mostly cylindrical 

 and serve in locomotion ; free-swimming. podoplea 



6 MU 



