LEAF-FOOTED GROUP 



3253 



segments of the thorax. The hinder border of this carapace is deeply cut out, and 

 near its front end there is a pair of contiguous compound eyes. The mouth is 

 bounded in front by a large upper lip and behind by a deeply cleft metastoma, or 

 lower lip. Both pairs of antennae are short. The jaws consist of a pair of 

 mandibles and two pairs of maxillae; these are followed by eleven pairs of thoracic 

 limbs, and there are appendages on the abdomen, sometimes numbering as many 

 as fifty-two pairs. The last segment of the abdomen bears a pair of long filaments, 

 and sometimes, as in Lcpidnrus, a distinct caudal plate. These crustaceans occur in 

 the fresh waters of most countries. They swim on their backs, using the legs as 



THE GLASSY LEPTODORA, Leptodora hyalina. 

 (Enlarged twelve times.) 



paddles; and the eggs are capable of surviving long periods of drought when 

 embedded in dried mud. In the second family the Branchipodidce the body is 

 also elongate, but there are no appendages to the abdomen, which consists of nine 

 segments, while there are eleven pairs of thoracic appendages. The headshield is 

 not developed backward, and the large separated eyes are supported upon distinct 

 stalks. In the male, the second antennae are converted into claspers. These forms 

 likewise swim upside down. Some (Branchipus) occur in fresh waters, but others 

 (Artcmia) prefer briny pools and flourish in water so strongly charged with salt as 

 to be fatal to other crustaceans. 



