312 AMIMIIPOUA NOUMALIA. 



flaj^cllum more or less articiilatcd. jraiitliljle having an appcnd- 

 ag'e. First pair of g-nathoi)o(ia sliort, tolcrahly robust ; caqnts 

 not having- the anterior margin interiorly produced ; second pair 

 having the carpus on the inferior angle anteriorly produced. First 

 pair of pereiopoda having the carpus dilated ; propodos narrow, 

 and capable of being inflected against the carpus : second pair hke 

 the first : third pair twice the length of tlio second ; carpiis veiy 

 long; propodos longer than the carpus, fringed along the anterior 

 margin with a comb-like series of teeth, and capable of impinging 

 against the anterior margin of the carpus : fourth and fifth pairs 

 subccpial, of the same form as the third, but not more than half the 

 length. Three posterior pairs of pleopoda subeqiial, the last being 

 the longest ; rami double, lanceolate. Telson small, squamose. 



Dana has placed this genus among the PHROsiNiNiE, or second 

 division of Pkuonimid.e, in his arrangement. It appears to me that 

 the progression is so gradual fi'om those species of Hyperia in which 

 the pereiopoda are of equal length, through those which are un- 

 equal, as in Hyperia oblivia, to the genera Vibilia, Cyllopus, and 

 Tliemisto, that no natural di^dsion exists where any separation can be 

 made with advantage, or without infringing upon other charactei's of 

 more importance. 



1. Themisto antarctica, (Plate L. fig. 8.) 

 Themisto antarctica, Dana, U. S. Explur. Expeil, p. 1005. pi. 69. f. 1. 

 Eyes reddish. Superior pair of antenna3 having the peduncle very short, 

 the second joint being covered by the first ; peduncle imiarticulate, 

 tapering to a point which is curved, like a strong hook ; joosterior 

 portion of the inferior margin furnished -ndth a longitudinal row of 

 small teeth or ttibercles, the inner margin furnished near the centre 

 with a longitudiniil row of long thick hairs; the superior margin near 

 the apex slightly villose. Inferior antennte about half as long again 

 as the superior, and furnished with a flagellum that is formed of one 

 long and seven short articuli. First pair of gnathopoda very short 

 and robust, having the carpus broad ; the propodos about half the 

 breadth of the carpus, the anterior portion furnished with a few 

 short stiff cilia, and a denticle which corresponds to the extremity 

 of the dactylos when shut against the propodos. Second pair of 

 gnathopoda having the carpus info ro-anteriorly produced nearly lo 

 the extremity of the propodos, with the inferior margin furnished 

 with a few hairs ; propodos tapering to the extremity, and furnished 

 with a few hairs on the superior margin; dactylos short and straight. 

 First pair of pereiopoda three or four times as long as the gnatho- 

 poda, having the meros short, triangular ; carpus broadly ovate, 



