THE GENUS LEBSRTIA. 489 



The epimera form a shield which may cover from one-half to 

 two-thirds of the ventral surface, and in young specimens may 

 even go as far as four-fifths, while in the case of gravid females 

 the proportions may be entirely reversed. A change of colour 

 also manifests itself, the prevailing tint being pale blue or violet. 

 The inner sutures between the first and second pairs of epimera 

 do not extend up as far as the exterior interval between the 

 second and third pairs, and in this respect it is much shorter 

 than Thor's type Jimbriata. The inner end of the second pair is 

 scarcely any broader than Jimbriata. The lateral expansions of 

 the third pair are large, while the inner ends of the fourth pair 

 are somewhat, though not much, broader than the outer ends. 

 The posterior edges of the epimera are not so thick as in some 

 species. The length of the legs appears to be approximately, first 

 pair, 0"80 mm. ; second pair, 0'90 mm. to 1'10 mm. ; third pair, 

 1*25 mm. ; and fourth pair, 1*50 mm. to 1*60 mm. The various 

 segments are comparatively long, markedly so in the three last 

 segments of the two last pairs of legs, so that the considerable 

 length of the legs is accounted for. The terminal segments are 

 not so robust. 



Thor has naturally compared the armature of the legs of this 

 species with that of his type Jimbriata, which he described in 

 detail. Although they have much in common, certain differences, 

 especially in the fourth pair of legs, are to be found. The out- 

 standing features of tau-insignita are as follows : the fourth 

 segment of the first and second pairs of legs has two or three 

 fine long bristles on the extensor surface. The third pair of legs 

 has three or four long pectinate bristles on the outer side 

 of the third segment ; the fourth segment has five bristles 

 similar to those of the first and second pairs of legs, and is 

 without swimming hairs. The fifth segment has three or four 

 shorter bristles standing close together, and has two swimming 

 hairs only. The greatest divergence is exhibited in the fourth 

 pair of legs. The second segment has two or three short bristles 

 distal on the extensor surface. The third segment has six 

 pectinate spines ranged round the distal extremity. The fourth 

 segment has six spines in a row on the flexor surface and one on 

 the inner surface. All are rather flattened at the extremity. 

 Six are pectinate, and swimming hairs are also wanting here. 

 The fifth segment has six short pectinate spines almost in a row 

 Journ. Q. M. C, Series II. No. 76. 34 



