Pacific Coast of North America, 261 



a'. Body narrow, scarcely depressed. Four anterior 

 pairs of legs unlike three posterior pairs, and not 

 ambulatory nor strictly prehensile, directed 

 forward, slender, ciliated, with terminal joint 

 minute ; last three pairs are stouter, ambulatory, 

 with terminal joint bifid X. Arcturid.b. 



Family IX. Idoteidse. 



Analytical Key to the Genera of Idoteidse *. 



a. Sides of head emarginate or cleft and laterally 

 produced beyond eyes, which are situated 

 upon its dorsal surface. Three anterior pairs 

 of legs, with penultimate joint or propodus 

 dilated and forming, with reflexible dactylus, 



a prehensile hand 17. Glyptonotiis. 



a'. Sides of head in a dorsal view entire and not 

 laterally produced. Eyes lateral. Legs all 

 ambulatory ; three anterior pairs with 

 penultimate joint not or not much dilated. 

 b. Flagellum of second pair of antennte well 

 developed and multiarticulate. 

 c. Palpus of maxillipeds four-jointed. Epi- 

 mera of all the segments well developed 

 and evident in a dorsal view. Abdo- 

 men t consisting of three t segments 

 with lateral sutures, indicative of 

 another partially coalescent segment . . 18. Idotea. 

 c' . Palpus of maxillipeds not four-jointed. 

 Abdomen consisting of one segment, 

 uniarticulate. 

 d. Maxillipeds with a three-jointed palp. 

 All the epimera coalesced and per- 

 fectly united with the segments .... 19. Synidotea. 

 d', Maxillipeds with a two-jointed palp. 

 Epimera of second, third, and fourth 

 segments coalesced and perfectly 

 united with the segments ; those of 

 the fifth, sixth, and seventh segments 



distinct and well developed 20. Colidotea, gen. nov. 



b' . Flagellum of second pair of antennte with 



joints all consolidated and forming a 



single piece, or with flagellum eomposed 



of only two or three joints. 



c. Body smooth, linear. Epimera of all the 



thoracic segments distinct and visible ; 



those of the second, third, and fourth 



segments short and narrow ; those of 



• See Miers on the Idoteidse, Journ. Linn. Soc. London, Zool. xvi 

 1883, pp. 9, 19, 20. _ 



t Including terminal segment. 



\ Dollfus, Feuille des Jeunes Naturalistes, 3° ser. 1895, p. 4: Sars 

 Crust, of Norway, 1897, pts. 3, 4, p. 79. ' 



