498 W. WILLIAMSON AND C. D. SOAR ON BRITISH HYDRACARINA : 



flexor surface, this appears to be more decidedly shown in 

 insignis (Thor's two figures do not agree as to this. Of. Zool. 

 Anz., xxviii. 821, fig. 1, and xxix. 788, fig. 53). All the short 

 fine hairs on the fourth segment are distal. 



The epimera are relatively larger than in sub-genus Lebertia. 

 As a rule the breadth is greater than the length. The lateral 

 extensions of the epimera embrace that portion of the sides 

 abutting on the epimera. It must be remarked here, however, 

 that these extensions can only be observed in certain positions 

 if the creature is not dissected. In preparations where the 

 epimera are removed, or the body is flattened out, the extensions 

 can be readily seen. The first pair of epimera is of normal 

 form. The second pair is narrow and of almost uniform 

 width throughout. If the suture between the third and fourth 

 pairs were continued for the full length, it would just about meet 

 the inner end of the suture between the second and third pairs, 

 showing the third pair to be almost triangular in form. The 

 fourth pair is broader at the inner end than at the outer. 

 The outer edge is lightly rounded. 



The legs measure up to 1*00 mm. in the first pair, 1*25 in the 

 second pair, 1*70 mm. in the third pair and 205 mm. in the 

 fourth pair. The fourth, fifth and sixth segments of each pair 

 of legs are much longer than the other segments. The sixth 

 segment of the second, third and fourth pair of legs is more 

 or less thicker at the distal extremity than at the proximal. The 

 first segment of the fourth pair of legs, which is much larger 

 than the corresponding segment of the other pairs, has on its 

 extensor surface one or two small proximal bristles and distally 

 two much longer ones. The flexor surface has one distal bristle 

 with two accompanying hairs. The flexor surface of the sixth 

 segment has generally only three spines. The swimming hairs 

 are short, relatively few and variable in number. The fifth 

 segment of the second pair of legs may have from five to seven. 

 With respect to the third and fourth pairs of legs, the fourth 

 .segment may have up to eight, and the fifth segment up to twelve. 



The genital area extends a little beyond the epimera. 

 Posteriorly it is bounded by a thick chitinous curving ridge and 

 anteriorly by a stellate sclerite which forms a bridge between it 

 and the epimera. The valves and acetabula are of normal form. 

 Along the inner edges of the valves there are a number of hair 



