ISOPODA 377 



3. EDOTEA Guerin. Second antennae of 4 to 6 segments and short ; 

 abdomen composed of a single segment; legs prehensile: 3 species. 



E. triloba (Say) (Fig. 600). Length 7 mm.; width 3 mm.: New 

 Jersey to Maine; under stones and decaying algae, in muddy places 

 along the shore. 



4. ERICHSONELLA Benedict. First antennae short ; second antennae 

 long and composed of 6 segments; abdomen composed of a single seg- 

 ment; legs ambulatory: 3 American species. 



E. filiformis (Say) (Fig. 601). Length 8 mm.; width 3 mm.: At- 

 lantic coast, south to Cape Cod ; in sand and among algae in shallow water. 



FAMILY 9. ASELLIDAE. 



Body flattened, with 7 free thoracic segments, and with the ab- 

 dominal segments forming a single, shield-like plate; abdominal append- 

 ages exclusively branchial and numbering 4 or 5 pairs; uropods terminal 

 and biramose: principally fresh-water animals; 17 American species. 



Key to the genera of Asellidae here described: 

 Oj Eyes present. 



6j Last 6 pairs of legs uniunguiculate 1. ASELLUS 



6, Last 6 pairs of legs biunguiculate 2. MANCASELLUS 



o a Eyes absent ; cave-dwellers 3. C^ECIDOTEA 



1. ASELLTTS Geoffrey. Abdomen about as broad as long; legs uniun- 

 guiculate; mandible with a palp: 7 American species; in fresh water. 



A. communis Say (Fig. 602). Length 15 mm.; breadth 5 mm.; first 

 antennae short, second long; first pair of legs prehensile and subchelate, 

 the others ambulatory, the last 3 being longer than the others: eastern 

 United States; the commonest 

 fresh-water isopod, occurring 

 generally among vegetation. 



2. MANCASELLUS Harger. 

 Abdomen about as broad as 



Inner- manrlihlp withnnt ft nnln- F te- 602 Diagram of Asellus communis, 



Ong, n B Wltnout a paip, show fe ing the int | rna l organs (McMurrich)' 



last 6 pairs of legs biun- J^-econd ^nna ; fJS&Sttlut 

 guiculate: 6 species; in fresh ^^ ^fg? ^ heart; 9 ' intes ' 

 water. 



M. macrourus Garman. Length 12 mm.; breadth 5 mm.; first pair 

 of legs subchelate, the others ambulatory ; side of the head cleft near the 

 eye: central United States east of the Mississippi, often in caves. 



3. CJECIDOTEA Packard. Body elongate and narrow; eyes wanting; 

 abdomen much longer than broad: 4 species; in caves and similar places. 



C. stygia Pack. Length 10 mm.; width 2 mm.; first pair of legs 

 prehensile, the hand being armed with 2 long and 3 short teeth: central 

 United States; in caves and deep wells. 



