SHELLED CBUSTAGEANS. 



the body and feet; 1-6 are the six lobes of the legs, to the 

 outer side of which arc attached the gill and the broad ac- 

 cessory gill {fb). 



The simplest Branchiopods are bivalved, and are usually 



Fig. \iil .—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 

 Plnjllopodd. In them (Fig. 107, Lim- 

 netis) and Estlicria (Fig. 108) the body 

 and legs are entirely concealed by the 

 large bivalve shell. In Apus (Fig. 109) 

 Fio,io8.-sheiiofaw,.rfaaiid Lepidurus (Fig. 110) the shield 

 shelled ig broad and flat, concealing but a 

 part of the body. In Brancliipus (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. Apiiis 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 



Belfragei; 

 Phyllopod. 



