15 



joint nearly twice as long as the other 2 combined, in male considerably 

 more elongated, and conrposed of 5 articulations successively diminishing in size, 

 the outer 2 representing the flagellum. Chelipeds in female of moderate size, 

 hand oval, with the fingers comparatively short, the thumb having, inside, 3 serra- 

 tions, the dactylus a single tubercle ; those in male of enormous size, carpus very 

 large and produced in front, outside the hand, to a lamellar lobe, hand imper- 

 fectly chelate, the thumb being transformed into a thin, reflexed lappet instricted 

 at the base, dactylus long and falciform, with 3 small denticles inside. First 

 pair of pereiopoda much larger than the others, the 3 posterior pairs more 

 strongly built than the 2 preceding ones, with the basal joint rather tumid. Uro- 

 poda about half the length of the metasome, inner ramus 4-articulate, outer very 

 small and biarticulate. Colour whitish. Length of adult female 2 mm., of male 

 about the same. 



Remarks. — ■ The very pronounced sexual difference occuiTing in the present 

 form has caused it to be twice described under 2 different names. Kroyer de- 

 scribed the female as Tanais Orstedi and the male as T. curculio, and some years 

 afterwards Fr. Midler, having apparently not been aware of Kroyer's description, 

 recorded the same form under 2 different names, viz. : Tanais balthieus (the female) 

 and T. rhynchites (the male). In this manner therefore, no less than 4 different 

 names have been assigned to the same species. As Kroyer was the first to 

 observe the species, one of his 2 specific names ought to be retained for the 

 species, and more properly that by which the female w r as described. From the 

 Mediterranean species, H. anomalus, the present form is easily distinguished by 

 the very different aspect of the male. 



Occurrence. — I have taken this form rather plentifully in the Iddefjord at 

 Fredrikshald, wln-re it occurred on a muddy bottom at a depth of 3— 6 fathoms. 

 Male specimens were, as usual, far less frequent than female ones, of which 

 numerous specimens, both young and adult, were collected. Some specimens 

 of this form are moreover contained in our University Museum, having been 

 taken by the late Dr. Boeck from piles of the quay at Christiansand. 



Distribution. — Oresund (Kroyer), Baltic at Landskrona and Westervik 

 (Lilljeb.), Prussia at Greifswalde (Fr. Midler), Bohuslan (Lilljeb.). 



