338 



CEUSTACEA 



Fig. 529 Fig. 530 



Fig. 529 Evadne nordmanni (Sharpe). 



A, female ; B, male. 

 Fig. 530 Podon leuckarti (Sharpe). 



Key to the genera of Polyphemidae here described : 



d Fresh-water animals 1. POLYPHEMUS 



o 2 Marine animals 2. EVADNE 



&! Head and thorax continuous dorsally. 



6 2 Head and thorax separated by a notch 3. PODON 



1. POLYPHEMUS 0. F. Miiller. 

 Head separated from thorax by a 

 dorsal depression: 2 species. 



P. pediculus (L.) (Fig. 528). 

 Length 1 mm.; body highly colored 

 but transparent : usually in deep lakes 

 and rivers; a back-swimmer; widely 

 distributed throughout America and 

 Europe. 



2. EVADNE Loven. Head and 

 thorax not separated by a dorsal depression; brood sac very high; 

 antennae small: 3 species; marine. 



E. nordmanni Lov. (Fig. 529). Outer branch of third pair of legs 

 with a single spine; length 1.15 mm. or less; colorless: very common 

 along the Atlantic coast. 



3. PODON Lilljeborg. Head and thorax separated by a dorsal depres- 

 sion: several species; marine. 



P. leuckarti (Sars) (Fig. 

 530). Length 1 mm.; both 

 branches of the second an- 

 tennae with 6 bristles each: 

 common along the Atlantic 

 coast occurring with the pre- 

 ceding; Europe. 



FAMILY 6. LEPTODORIDAE. 



Shell rudimentary and not covering the 

 legs or the long, segmented abdomen; 6 

 pairs of cylindrical legs, the first pair 

 being much larger than the others; 2 ter- 

 minal claws on the abdomen: 1 genus. 



LEPTODORA Lilljeborg. With the 

 characters mentioned above: 1 species. 



L. hyalina Lillj. (Fig. 531). Body elongate; first antennae small 

 in female, but very long in male; length 9 mm.; transparent: in clear 

 fresh-water lakes in America and Europe; it comes to the surface usually 

 only on dark nights. 



Fig. 531 Leptodora 

 hyalina. 1, first anten- 

 na ; 2, second antenna ; 

 3, shell. 



