376 



CRUSTACEA 



Family 8. IDOTHEIDAE. 



Body more or less broad and flattened; often elongate; abdominal seg- 

 ments partially or completely fused ; uropods lateral, arching over and cov- 

 ering the other pleopods mider the abdomen : about 90 species, 40 American. 



Key to the genera of Idotheidae here described : 



Oi Side of head cleft and extending beyond eyes 2. CniRiDOTEA 



Oo Side of head not extended in dorsal view. 

 6i Second antennae with a long flagellum ; abdomen of several segments, 



1. Idothea 

 62 Second antennae without a long flagellum ; abdomen a single segment. 



Ci Second antennae not much longer than head 3. Edotea 



Ci Second antennae very much longer than head.. 4. ERicnsoNELiA 



1. Idothea Fabricius. Second antennae with a long flagellum and much 

 larger than the first; legs all alike; abdomen composed 

 of 3 complete and 1 partial segment : 8 American species. 

 I. baltica (Pallas) (I. marina L. ; I. irrorata Say) 

 (Fig. 598). Length 20 mm.; width 7 mm.; color often 

 green, but very variable; abdomen ending in three projec- 

 tions: Nova Scotia to North Carolina; cosmopolitan; on 

 seaweed, in sand or at the surface; common. 



I. phosphorea Harger. Length 21 mm. ; width 7 mm. ; 

 color variable; abdomen tapering to a point: coast of 

 New England, among rocks and seaweed. 



I. metallica Bosc (/. rohusta Kroyer). Length 18 

 mm.; width 8 mm.; abdomen truncate: entire Atlantic coast; cosmo- 

 politan; often on floating seaweed. 



Fig. 598 



Idothea baltica 



(Harger). 



Fig. 599 Fig. 600 Fig. 601 



Fig. 599 — Chiridotea cOBca (Harger), Fig. 600 — Edotea triloba (Harger). 

 Fig, 601 — Erichsonella fiUJormis (Harger). 



2. Chiridotea Harger. Second antennae usually with a short fla- 

 gellum, sides of head cleft at the eye and extending beyond it; first 3 

 pairs of legs prehensile, last 4 pairs ambulatory; abdomen composed of 

 4 segments: 2 species. 



C. caeca (Say) (Fig. 599). Body ovate, with a long, pointed telson; 

 length 8 mm. ; width 4 mm. ; antennae of nearly equal length ; eyes small, 

 dorsally placed: Florida to Nova Scotia; at the surface or in the sand. 



