348 CEUSTACEA 



to 10-jointed, in the male modified and prehensile ; second antennae usually 

 biramose; fifth pair of feet 1 or 2-jointed and serving as egg support in 

 the female; heart absent; usually a single egg sac present: about 30 

 genera and 150 species, mostly marine, usually found among vegetation. 

 Key to the genera of Harpacticidae here described : 



0,1 Fresh-water animals ................................ 1. CANTHOCAMPTUS 



O 2 Marine animals. 



&! The outer branch of the first pair of legs much longer than the inner. 



2. HARPACTICUS 



6 2 The inner branch longer than the outer ................... 3. ECTINOSOMA 



1. CANTHOCAMPTTTS Westwood (Fig. 549). Thorax of 4 segments; 

 head with a rostrum; first antennae with 6 to 9 joints, usually 8 in the 

 female; abdomen 5-jointed in the male and 4 in the 

 female: mostly in fresh water; about 6 American species. 



C. minutus Glaus. Body 1 mm. long; first antennae 

 8-jointed; legs 3-jointed in both branches, except the 

 fifth leg, which is 2-jointed: eastern and central states; 

 common, especially in muddy pools; Europe. 



2. HARPACTICUS Milne-Edwards. Outer branch of 

 the first leg 3-jointed, almost twice as long as the 2-jointed 

 inner branch; conical rostrum present; third pair of legs 

 with very strong outer branch: 12 species; marine. 



H. chelifer (0. F. Miiller). Length of male 1 mm.; 

 first pair of legs with 1 spine, outer branch with 3; inner 

 caudal spines longer than the cephalothorax : Atlantic 



cactus C0ast ; Eur P e ' 



F.St). 3 * E CTINOSOMA Boeck. First antennae 5 to 7-jointed; 



first pair of legs scarcely smaller than the others and with 

 the inner branch longer than the outer; fifth pair of legs 2-jointed: 12 

 species. 



E. curticorne Boeck. Length .7 mm.; color dark brown; first an- 

 tennae very short, 6-jointed: common in Narragansett Bay; Europe. 



4. PARATEGASTES G. 0. Sars. First antennae 6 or 7-jointed; second 

 antennae with a 1-jointed outer branch; last pair of legs very large in 

 the female, with an expansion on the basal joint. 



P. sphaericus Glaus. Length .35 mm.; color brown: abundant in 

 Narragansett Bay; Europe. 



FAMILY 6. EEGASILIDAE.* 



Body more or less cylindrical, somewhat like Cyclops in shape, 

 usually well segmented ; first pair of antennae 5 to 7-jointed, second 3 or 



* ''North American Parasitic Copepods Belonging to the Family Ergasilidae," by 

 C. B. Wilson, Proc. U. S. Nat. Mus., Vol. 39, p. 263, 1911. 



