SHELLED CRUSTACEANS. 
89 
the body and feet; 1-6 are the six lobes of the legs, to the 
outer side of which are attached the gill and the broad ac- 
cessory gill 
The simplest Branchiopods are bivalved, and are usually 
Fig. \07.—Limnetis brevifrons. Much enlarged. 
less than a tenth of an inch in length. They are called 
Ostracoda, 
Eather larger forms are the water-fleas {Daphnia), which 
represent the sub-order Cladocera. 
The most interesting sub-order is the 
Pliyllopoda. In them (Fig. 107, Lim- 
7iefis) and Estheria (Fig. 108) the body 
and legs are entirely concealed by the 
large bivalve shell. In Apus (Fig. 109) 
FIa.l08.-Shellof^.f/^.r^a ^^^^'i LepidurUS (Fig. 110) the shield 
Ph/nSpod ^ s^^ii^d is broad and flat, concealing but a 
part of the body. In BrancMpus (Fig. 
Ill), which is common in roadside pools and in ponds in 
the cooler parts of the year, there is no carapace. The 
Phyllopods swim on their backs. Apiis is remarkable for 
having 47 segments in all, and 60 pairs of limbs; certain 
segments bearing as many as six pairs of limbs. All the 
