300 MANUAL OF NATURAL HISTORY. 



branous, always ending in two oars each, composed 

 of two or more joints. 



I. ORDER — Ostracods (Ostracoda). 



Body enclosed in a bivalve carapace ; first pair of 

 antennae setaceous, second pair very large, forming 

 natatory oars ; two posterior pairs of jaws with a 

 large fan-shaped appendage. 



1. Family. — Gyprises (Cypridse). A single large 

 eye on upper part of face ; abdomen conical, 

 ending in two styles ; two pairs of slender 

 legs. 



II. ORDER — Copepods (Copepoda). 



Body divided into several segments, not enve- 

 loped in a bivalve test ; furnished with foot-jaws, 

 and with four or five pairs of legs. 



1. Family — Pontias (Pontiidse). Eyes two, dis- 



tinct, non-pedunculated ; body oval, ending 

 in a narrow prolongation ; head distinct, 

 armed in front with a moveable rostrum. 



2. Family. — Gyclopses (Cyclopidas). A single eye 



situated on the middle line at fore and upper 

 part of head ; head indistinct, with no move- 

 able rostrum ; abdomen elongated. 



III. ORDER— King-Crabs (Xyphosura). 



Jaws replaced by the basal part of the six pairs 

 of fore-legs, which are furnished at that part with 

 minute teeth ; hind-legs serving for respiration. 

 ] . Family. — King - Grabs (Limulidse). Carapace 



