MANUAL OF NATURAL HISTORY. 299 



of more than eighteen pairs ; abdomen nar- 

 row, cylindrical. 

 3. Family. — Pond-Shrimps (Branchipidae). Body 

 elongated, without a bivalve or scutiform 

 carapace ; eyes pedunculated ; nine pairs of 

 branchial feet. 



II. ORDER — Lophyropods (Lophyropoda), 



Body enclosed between two valves ; feet four or 

 live pairs, foliaceous. 



1. Family. — Water-Fleas (Daphniidae). Head dis- 



tinct, prominent, prolonged below into a 

 beak ; a single eye on anterior part ; upper 

 antennae in the form of large oars ; abdomen 

 conical. 



2. Family. — Polyphemuses (Polyphemidae). Head 



very large, nearly all occupied by a single 

 great eye ; upper antennae very large, ending 

 in two branches with long hairs ; feet four 

 pairs ; abdomen recurved, not lodged in valves 

 of carapace. 



3. Family. — Beaked Water-Fleas (Lynceidae). Head 



small, curved below in form of a beak and 

 prolonged posteriorly over back ; a single 

 eye ; antennae short ; valves of carapace very 

 large. 



IV. LEGIOK — Entomostracans (Entomostraca). 



Gills none ; eyes sessile ; mandibles adapted for 

 mastication ; feet natatory, not foliaceous, or mem- 



