80 



E. Miers 1 ), the genus comprises, in my opinion, forms which can hardly be placed 

 in one and the same genus. As to the Norwegian Idothea?, they have generally 

 been considered by recent authors as only varieties of one and the same species. 

 A closer examination of the large material at my disposal has, however, shown 

 them in reality to be referable to no less than 6 different species, all easily re- 

 cognizable in both sexes. 



l. Idothea baltiea (Pallas). 



(PI. XXXII.) 



Oniscus baUicus, Pallas, Spic. Zool. Vol. IX, p. 06. PL IV, fig. 6. 



Syn: Stenosoma irroratct, Say. 



„ Idothea tricuspidat"., Desm. 

 „ — trideniata, Rathke. 



„ — irrorata, Harger. 



„ — marina, Miers. 



Specific Characters. — Body oblong oval, about 3 times as long as it is 

 broad, with the dorsal face perfectly smooth. Coxal plates rather large, occupying 

 the whole length of the side-edges of the segments, so as to form a broad, conti- 

 nuous marginal area. Metasome about the length of the 5 posterior segments 

 combined, terminal segment slightly tapering distally, side-edges straight, tip dis- 

 tinctly tridentate, middle tooth conically produced, lateral ones much shorter, 

 though well defined, and each separated from the median tooth by a well-marked 

 sinus. Eyes of moderate size, rounded. Superior antenna? with the 1st joint of 

 the peduncle rather broad, irregularly angular, last joint much longer than the 

 middle one, flagellum about the length of the former. Inferior antenna? rather 

 elongated, reaching, when reflexed, almost to the end of the 3rd segment of meso- 

 some, flagellum very slender, being much longer than the peduncle, and composed 

 of from 16 to 20 articulations. Legs moderately strong, being, as. usual, more 

 powerfully developed in male than in female. Stylet of the 2nd pair of pleopoda 

 in male not extending to the end of the inner plate. Uropoda with the terminal 

 plate obtusely truncated at the tip. ( Colour extremely variable, sometimes uni- 

 formly yellowish or greenish with small dark dots, sometimes variegated, with 

 dark brown pigment forming regular longitudinal bands or larger patches arranged 

 in a perfectly symmetrical mannerJ Length of adult male reaching to 35 mm. 



MemarJcs. — Mr. E. Miers names this form Idothea marina, believing that 

 Linnseus' Oniscus marinus refers to this species. This is, however, very doubtful, 

 and as that specific name has been -more properly applied to another Isopod, 



') Revision of the Idoteidse. Linn. Sou. Journal. Zoology, Vol. XVI. 



