!g CRUSTACEA MALACOSTRACA. III. 



Thoracic segments on the whole somewhat similar to those in /. alia, yet presenting some 

 sharp differences. First segment has its lateral lobe much narrower than in I. alia, obtuse, as broad 

 as, or a little broader than, the epimeral process, which is longer than the lobe, a little curved, acute. 

 Second and third segments have their lateral plates divided into two lappets by a broad, moderately 

 deep incision with two angles; each lappet is somewhat small and distally rounded, and in each 

 incision are seen two epimeral protuberances, the anterior small and rounded, the posterior much 

 smaller. Fourth segment differs from the third in having its anterior lateral lappet distinctly larger, 

 while the posterior is wanting; the epimeral plate has a well developed anterior protuberance, while 

 the posterior is small or wanting. The lateral plates of the three posterior segments are small and 

 rounded, excepting those of seventh segment, which are produced behind into an acute triangle; the 

 epimeral protuberances at these segments are small but easily seen from above. 



The abdomen (fig. 3 a) has each postero-lateral part broadly rounded or subtriangular and pro- 

 duced slightly beyond the flatly convex part of the hind margin between the uropods. The 

 posterior half of each lateral margin (fig. 3 b) is adorned in a most peculiar way, showing some five 

 or six broad and moderately low incisions with a small protuberance terminating in a more or less 

 strong seta at the middle of each incision; each lappet between two incisions is broad or very broad 

 and its rather short lateral margins concave, with the result that the lappet is narrower at the middle 

 than at its nearly straight distal margin. — The uropods about as long as the abdomen. 



Length of the largest specimen, an ovigerous female (from Holstensborg) 8-6 mm. 



Remarks. I. tricornis is easily distinguished from the two preceding species by the antero- 

 lateral processes of the head, each terminating in an articulated spine, by several points in the shape 

 of the thoracic lateral lobes and the epimeral protuberances, and by the curious adornment of the 

 lateral margins of the abdomen. — Kroyer's detailed description is good, but he had evidently examined 

 a female which had the uropods anomalously small, while as a rule the uropods have the same length 

 in both sexes. I have found very few specimens of various species of the genus Ianira with either 

 both uropods small, or one uropod much smaller than the other. 



Though Ortmann's figure of his Tole (Iole) libbeyi is very poor, Stephenseu's interpretation is 

 certainly correct, but the latter author overlooked the fact that the animal belongs to the Kroyerian species. 



Occurrence. Taken by the "Ingolf" at three places. 



Davis Strait: Stat. 29: Lat. 65°34' N., Long. 54°3i' W., 68 fath., temp. 0-2°; 3 spec. 



Stat. 34: Lat. 65°i7' N., Long. 54°i7' W., 55 fath.; 1 spec. 



Mouth of Ameralik Fjord, Lat. 64°c>3' N., 5—70 fath., shells; 5 spec. 



It has been taken many times at West Greenland from Lat. 78° N. to Lat. 6o°4o' N., and several 

 of the localities have been recorded in the literature (H. J. Hansen, Ortmaun, Stepheusen). The localities 

 may be briefly enumerated: Cape Alexander, 27 fath.; Disko Bay; Huude-Eiland ; Egedesminde, 25, 

 30—40 and 40 fath.; Northern Stromfjord, 7—20 fath.; Holstensborg, 40 fath.; Sukkertoppen, 30 fath.; 

 Lat. 65°n' N., Long. 53°33' W., 50 fath.; Kangerdluarsuk, 5—15 fath., finally not far from Julianehaab, 

 22 fath. (many collectors). 



At East Greenland it has been taken by the 1st Amdrup Exped. at Tasiusak, Lat. 65°37' N., 



