ME. E. J. MIERS ON THE IDOTEIDiE. 41 



a median dt)rsal keel. Head nearly smooth, its antero- lateral 

 angles rounded and not prominent, and its anterior margin very 

 slightly sinuated or nearly straight, the impressed line near the 

 posterior margin faintly marked or quite obsolete. The first 

 thoracic segment has its antero-lateral angles anteriorly pro- 

 duced and broadly rounded, the two following segments less 

 distinctly so ; all the thoracic segments are of nearly equal length 

 in the median dorsal line. The terminal postabdoniinal segment 

 is convex, not 1^ times as long as broad, bluntly rounded at its 

 distal end, with a small blunt median terminal tooth, posterior to 

 which is usually iadicated a longitudinal median keel, wliich 

 is prolonged backward for a short distance on the dorsal surface 

 of the segment. Eyes small. Antennules very short, not reaching 

 to the distal end of the antepenultimate joint of the peduncle of 

 the antennae. The antennae, when retracted, do not surpass the 

 posterior margin of the third thoracic segment; the last two joints 

 of the peduncle are short, subequal, each scarcely longer than the 

 antepenultimate joint; flagellum 12-14-jointed. Epimera of 

 second to fourth thoracic segment nari'ow-linear and not reaching 

 quite to the postero-lateral angles of these segments ; the epimera 

 of the fifth to seventh thoracic segments become successively 

 broader, and reach to the postero-lateral angles of the segments. 

 The terminal joints of all the legs are usuallj' armed with a 

 small accessory claw ; the terminal plates of the operculum are 

 not oblong, but have their exterior margins regularly arcuated. 

 Length of an adult male about 1| inch (82 millim.), breadth 

 about Y^^ inch (11 millim.). 



This species ranges from the Sea of Ochotsk and Kamtchatka 

 Sea, along the western coast of North America, to the coast of 

 California. 



Specimens are in the British-Museum collection, preserved dry, 

 from Vancouver's Island (J. K. Lord, as I. WosnesensJcii and 

 I. media), and in spirit (of both sexes) from Skedegate Bay, 

 Queen Charlotte Island (purchased of Dr. Brown) ; also a male 

 from Fort Eupert (Dr. Brown), and three males from San Fran- 

 cisco, California (W. N. Lockington, as I. WosnesensJcii). 



In the Paris collection is an adult male of large size, with very 

 robust and hairy legs, from Unalaschka, three examples from 

 California (with /. WMtei), and two small specimens, Avithout 

 locality, designated I. oregonensis ; also a good series from the 

 Grulf of Georgia (A. Agassiz). 



