igil] NORDAMERIKANISCHE HYDRACHNIDEN. 291 



marginal hairs (Fig. 16). The third segment, which is 50/x long, is shorter 

 than the second (length 65/Lt) ; the length of the whole palpus is 240/t. 

 The bristle on the flexor side of the second segment is stout, straight, not 

 pectinate, and shorter than the segment. The inner surface of the third 

 segment bears six fine bristles, of which three are borne upon the distal 

 margin, one upon the proximal margin, and two approximately on the 

 middle of the extensor surface, close to each other. On the outer end of 

 the penultimate segment internally is a spine-like, chitinous process. 



The epimeral region, which is about 500/i. in length, extends 50/j, be- 

 yond the frontal margin of the body and leaves the ventral abdominal 

 surface uncovered only to the extent of a space 132/u, long; its breadth 

 is not less than that of the body. 



The genital emargination, the length of which is i66fi, is considerably 

 longer than the maxillary emargination, which is only ii6fi long. The 

 common posterior end of the second pair of epimera is 33^ broad. The 

 median suture of this pair of plates is a little shorter than half the dis- 

 tance between the maxillary and genital emarginations. The last plate 

 has a considerable size and is narrower externally than internally, ter- 

 minating behind in an irregular curve ; its postero-internal angle projects 

 considerably toward the genital organ, though not to the same extent as 

 obtains in L. complexa Koen. The articular fossa of the posterior leg 

 is situated far from the outer margin of the epimeron (Fig. 13). 



The lengths of the legs measured in series from first to last are as 

 follows: 464, 531, 614, iSoyLi. The legs are all of the same thickness, on 

 the whole moderately stout, becoming only slightly slenderer towards 

 the distal extremities. The tarsi of the three posterior pairs are slightly 

 enlarged at the distal extremity, the ungues correspondingly larger than 

 those of the anterior legs ; those of the latter are 20, of the remaining legs 

 30-35/i long. The ungual plate (Krallenblatt) is 15/i broad, the acces- 

 sory tooth considerably shorter than the principal one. The leg bristles 

 consist on the whole of spines of different lengths, mostly arranged in 

 circlets at the outer ends of the segments ; the largest and stoutest occur 

 on the second pair of legs; fine hairs are sparingly present on the front 

 pairs. Swimming hairs, even vestigial ones, are entirely absent. 



The genital area is 140/i long, 83/* broad behind and completely 

 withdrawn into the genital emargination. The elliptical ace tabula differ 

 but little from one another in size (Fig. 13). The sex of the imago here 

 described was not recognized. 



The anal aperture is near the posterior margin of the body, from 

 which it is distant by about its own posterior breadth. It lies a little 

 behind the level of the anal glands. There is no distinct anal area. 



Among the species of Lebertia with 6 bristles on the inner side of 



