56 REPORT OF NEW JERSEY STATE MUSEUM. 

 Key to the families. 



a. Rami of both antennas three-jointed; intestine convolute, with abdominal 



but no anterior caeca. lynceid^ 



aa. Rami of antennae three and four-jointed; five pairs of feet, last with 



curved appendage guarding branchial sac; antennules of female short, 



one-jointed. daphnid^ 



Family EYNCEID^. 



Head covered with an arched shield, this often passing without 

 an indentation into the shell of body. Head covering generally 

 extending forward and downward to form more or less of sharp 

 angle in front, or simply rounded. In either case it arches over 

 more fleshy lower side of head, from which hang two short 

 antennules and labrum, while strong two-branched antennae 

 spring from well up under its posterior expansion. Rounded 

 sides of shield, which protect insertion of antennae, known as 

 fornices. Above insertion of antennae a dark fleck lying near or 

 on lower angle of brain, which is the larval or nauplius eye. This 

 black spot often large as eye itself, even larger, and sometimes 

 the only visual organ. Antennules small, with several sensory 

 filaments, and a lateral flagellum at end. Antennules in male 

 dififering little from those of female. Labrum with triangular 

 or semicircular process, and usually larger than tenninal portion. 

 Mandibles similar to, though usually shorter, than in Daphnidce. 

 Maxillae often conspicuous, and first pair of feet serving by slight 

 alteration at base same purpose. Rarely an indication of sixth 

 pair of feet, and antennae with both rami three-jointed. End of 

 body, or post-abdomen, usually enlarged, anal opening near its 

 base, and armature usually considerable. 



Genera numerous, comprising very small species, and but few 

 exceed one millimeter in length. The shell is various in form, 

 often beautifully sculptured. A limited number of eggs is pro- 

 duced at one time and the winter eggs are very often laid in the 

 brood-cavity with no preparation of the shell previously, in 

 which case the ephippium is said to be absent. Negatively, the 

 shell may be considerably modified, generally with a deposit of 



