AMPHIPODA 369 



Calliopiits Lilljeborj^. Both pairs of gnatliopods large and of 

 equal size; terminal abdominal segment slender and not split: 2 species. 



C. laeviusculus (Kroyer) (Fig. 581). First and second antennae of 

 nearly the same length; eyes large; length 16 mm.; color light green: 

 Cape Hatteras to Greenland, in tide pools 

 and among seaweed; Europe; North Pacific. 



Family 5. GAMMAEIDAE. 



Both pairs of antennae long, the first 

 antennae usually longer than the second and 

 with a secondaiT flagellum which is a small ^^^' ^^VfrauimS'r!^ "'"'''"' 

 side branch of it; mandible with a palp; 



both pairs of gnathopods usually of the same size; terminal pleopods 

 extending beyond the others: over 50 genera and 250 species, largely in 

 fresh and brackish waters. 



Key to the genera of Gammaridae here described : 



a^ Last 3 abdominal segments with small bunches of hairs along hinder margin. 



6i First 3 abdominal segments not extended behind 1. Gammarus 



62 First 3 abdominal segments each extended behind as an acute tooth. 



2. Carinogammarus 



Oa No such bunches of hairs on these segments 3. Elasmopus 



1. Gammarus Fabrieius. Telson deeply cleft; last 3 abdominal seg- 

 ments with bunches of small hairs: over 30 species; in salt and fresh 

 water; 6 fresh- water species in the United States. 



Fig. 582 Fig. 583 



Fig. 582 — Gammarus locusta (Paulmeier). Fig. 583 — Oammarus faciatus (Paulmeier). 



G. locusta (L.) (Fig. 582). First antennae longer than the second; 

 secondary flagellum with about 8 joints; length 20 mm.; color greenish: 

 Arctic Ocean to New Jersey, being very common under stones and in 

 seaweed along the seashore; Europe. 



G. annulatus S. I. Smith. First antennae shorter than the second; 

 length 15 mm.; no lateral hairs on the fourth abdominal segment: Long 

 Island Sound to Bay of Fundy. 



