14 



Tanais, on separate lobes. Superior antennas in female short, triarticulate, with 

 only a single terminal olfactory filament, in male more elongated, with the flagel- 

 lum more or less developed. Mandibles rather strong, cutting edge in the left 

 one consisting of 2 superposed dentated lamellae, in the right mandible simple 

 and finely serrated on the front edge, molar expansion in both mandibles large 

 and thick. Palp of anterior maxillae uniarticulate, terminating with 2 setae only. 

 Epignath of maxillipeds narrow falciform. Oral parts in male quite abortive. 

 Chelipeds in female normal, in male very different, being imperfectly chelate, 

 thumb very short, or transformed to a posteriorly-pointing lappet. 1st pair 

 of pereiopoda longer than the others, with the dactylus setiform; the succeeding 

 ones comparatively short and stout, with the dactylus simple. Pleopoda normal. 

 Urovjoda biramose, outer ramus very small, inner elongate, 4 — 5 articulate. In- 

 cubatory j)ouch normal. 



Remarks. — This genus was established by the present author in 1880, to invlude 

 Tanais Orstedi of Kroyer, which in some points differs rather markedly from the 

 other Tanaidse, though being most nearly allied to the genus Leptochelia of Dana. 

 From the latter it differs chiefly in the very anomalous structure of the chelipeds 

 in the male. Besides the typical form, another species has been described by 

 the present author from the Mediterranean as H. anomalus. Moreover, the north 

 American form Leptoclielia limieola Harger, and the New Zealand species Paraianais 

 tenuis Thomson, are most probably referable to this genus. 



Heterotanais Orstedi, Kroyer. 



(PI. VI.) 

 Tanais Orstedi, Kroyer, Nat. Tidsskr. Bd. 4, p. 183. 

 Syn : Tanais curculio Kroyer d*. 

 ,. „ balthicus Ft. Miiller 9- 



„ ,, rhynchites Fr. Jluller cf. 



Specific Characters. — Body about 5 times as long as it is broad, with the 

 cephalosome in female of normal appearance, equalling in length the 3 succeeding 

 segments combined, in male strongly produced and abruptly narrowed in front 

 to a cylindrical neck, carrying on the tip the antennas and eyes. Segments of 

 mesosome much more densely crowded in male than in female. Metasome in 

 male about half the length of the mesosome, in female scarcely longer than the 

 last 2 segments combined, terminal segment comparatively short and obtusely 

 rounded at the tip. Eyes of moderate size and same appearance in the two 

 sexes. Superior antennse in female shorter than the cephalosome, with thehasal 



