APPENDIX TO CHAPTER VIII 131 



APPENDIX TO CHAPTEE VIII 



KEY TO THE FIVE ORDERS OF ENTOMOSTRACA 



a\. Free-living or parasitic inhabitants of the sea or 



of fresh water. 

 61. 2 pairs of maxillae. 



ci Mandible without palp ; 4 or more pairs 

 of foliate swimming legs behind maxillae 

 [Phyllopoda]. 

 d\. With 10 to 40 pairs of legs . . Sranchiopoda 



(Ex. Branchipus) 



eZ 2 - With 4 to 6 pairs of legs . . . Cladocera 



(Ex. Daphnia) 



Co. Mandible with leg-like palp ; only 2 pairs 



of appendages behind maxillae . . Ostracoda 

 bo. Only 1 pair of maxillae, followed by 4-5 pairs 

 of bifid, oar-like feet ; often deformed as a 

 result of parasitism . . . ... Copepoda 



(Water-fleas) 



a 2 . Sessile marine animals, whose body is surrounded 

 by a usually calcified mantle ; 6 pairs of tendril- 

 like feet Cirripedia 



(Barnacles) 



Key to the principal families of Cladocera, to which group Daphnia 

 belongs : 



a\. Body enclosed in a bivalve shell ; mandibles trun- 

 cate below ; maxillae distinct, spiny. 

 61. 6 pairs of similar, foliaceous, distinctly 

 branchiate feet ; swimming antennas with 

 2 unequal rami ; intestine straight . . . Sididce 



5 2 . 5 (or 6) pairs of feet, the anterior pair more 

 or less prehensile and destitute of branchiae. 

 GI. Rami of antennae 3- and 4-jointed ; 5 

 pairs of feet, the last with a curved 

 appendage guarding the branchial sac ; 

 antennules of the female sort, 1-jointed Daphnidce 



