COPEPODA 341 



land coast, a widely spread, pelagic species, sometimes so abundant that 

 the sea is colored yellow or red, and of great economic importance 

 because it forms an important source of food of herring and mackerel, 

 as well as of the Greenland whale. 



C. minor Glaus. Length about 1.8 mm. ; thorax of 4 segments ; fifth 

 pair of legs biramose; 

 first antennae not as long 

 as the body: Gulf stream, 

 off New England, a wide- 

 ly spread species. 



2. CALOCALANUS 

 Giesbrecht. Thorax of 

 female consists of 3 seg- 

 ments, the first somite 

 being fused with the 



head, and the fourth with 



Fig. 533 Calocalanus pavo (Wheeler), 

 the fifth somite; abdo- 

 men of female of 2 or 3 segments; abdomen of male of 5 segments; 

 caudal spines very long and plumose: 3 species. 



C. pavo (Dana) (Fig. 533). Abdomen of female of 2 segments; 

 caudal bristles symmetrical, branched, and spreading; length 1 mm.; 

 body transparent and reddish : a tropical species which may be found in 

 the Gulf stream oft' New England. 



FAMILY 2. CENTKOPAGIDAE.* 



Body elongate; first antennae very long, with 23 to 25 joints in the 

 female; the right one (sometimes the left) in the male being prehensile; 

 second antennae large and biramose; heart present; first 4 pairs of legs 

 biramose, the outer branch being 3-jointed, the inner branch 1 to 3- 

 jointed; fifth pair of legs biramose, often modified for clasping; a single 

 egg sac present : about 25 genera and 200 species ; in salt and fresh water. 



Key to the genera of Centropagidae here described : 

 Oi Marine animals. 

 &! First antennae with 24 segments. 



Cj Thorax of 5 segments ; 1. CENTBOPAGES 



c 2 Thorax of 4 segments 2. TEMOBA 



6 2 First antennae with 23 segments 3. METBIDIA 



a z Both marine and fresh-water animals. 

 &! First antennae with 25 segments; fifth feet biramose. .. .4. LIMNOCALANUS 



6 2 First antennae with 24 segments ; fifth feet uniramose 5. EUBYTEMORA 



a 3 Fresh-water animals ; first antennae with 25 segments. 



&! Fifth feet uniramose ; abdomen asymmetrical 6. EPISCHUBA 



6 2 Fifth feet b^ramose ; inner branch of first pair of feet 2-jointed. 



7. DlAPTOMUS 



* See "The North American Centropagidae," etc., by F. W. Schacht, Bull, of 111. 

 St Lab., Vol. 5, p. 225, 1898. 



