344 



CRUSTACEA 



of abdomen; ceplialothorax widest in the middle: widely distributed and 

 common over the entire northern part of the country. 



D. leptopus Forbes (Fig. 539). First antennae about as long as the 

 body; thorax of 4 segments; length 1.5 mm.; body transparent, with pur- 

 ple bands, especially on the terminal portion of the antennae and the 

 abdomen: common in the central states. 



D. sanguineus Forbes. Body bright red and 2 mm. long; last tho- 

 racic segments with strong lateral spines, and a dorsal hump; first 

 abdominal segment with strong lateral spines: central and eastern United 

 States ; common ; it occurs only in the early spring, in stagnant pools. 



D. minutus Lilljeborg. Body small, l.mm. long, and slender; thorax 

 of 4 segments ; antepenultimate joint of first antennae with a long slender 

 process ; terminal hook of right fifth feet in male broad : common in the 

 Great Lakes and widely distributed in northern America; Europe. 



Family 3. PONTELLIDAE. 

 Body elongate, with 4 thoracic segments; first antennae very long, 

 the right one in the male being prehensile; second antennae large and 

 I 



<^^ 



Fig. 540 Fig. 541 



Fig. 540 — Tortanus ftetacaudatus (Williams). A, dorsal aspect of female; B, 

 abdomen. Fig. 541 — Lahidooera <r!^tira (Wheeler). A, dorsal aspect of female; 

 B, lifth leg of male ; C, right fifth leg of female. 



biramose; first pair of legs weak or rudimentary; heart present; median 

 eye and also often paired eyes present; but 1 egg sac: 10 genera and 

 over 70 species; marine. 



Key to the genera of Pontellidae here described : 



a, First antennae 23-jointod 2. Labidocera 



ffj First antennae 17-jointo(l. 



7>, The 2 branches of the second antennae of equal length 1. TouiWMis 



^2 These branches of unequal length 3. Acartia 



1. Tortanus Giesbrecht. First antennae of female 17-jointed ; abdo- 

 men of female consists of 2 or 3 and of the male of 5 segments; the 2 



