2S6 Transactions of the Canadian Institute. [vol. ix 



porous, the breadth of the porous area behind the latter being about 50/*. 

 The large processes do not extend backwards beyond the hind margin 

 of the maxillary shield and are moderately thickened at their free ex- 

 tremities. 



The tracheal plates extend beyond the pharynx ; they are of consider- 

 able breadth and moderate height and are perfectly straight except at 

 their free extremities which are slightly curved upwards. 



The pharynx, which is only about 50/^ broad at the anterior end, 

 widens caudad to 175/"- at the slightly-developed, transverse, chitinous 

 arch; its lateral margins are convex. The posterior end including the 

 chitinous arch appears triangular in ventral view. The mandible is 

 232/x. long, the basal segment about 150^11. broad in front. The posterior 

 angle of the flexor side is very obtuse, so that the flexor and posterior 

 sides present a regularly curved margin and the basal segment appears 

 to run out behind into a point (angle of the hind margin of the extensor 

 side). The antero-lateral margin of the flexor side is straight. 



The maxillary palpus has on the whole a slender form. It is 762/A 

 long and the individual segments, taken in series from the first to the 

 fifth, are 66, 116, 149, 265 and 166/j, long respectively. The second joint, 

 whose cuticle is thin on the flexor side, bears on its inner anterior margin 

 only three bristles, two near together towards the flexor surface and one 

 on the extensor surface. The third palpal segment is quite slender at 

 base, but at the opposite end extremely thick, owing to the unusually 

 stout prominence on the flexor side; the latter bears a group of short 

 spines. On the outer side the same segment has an oval opening 85/x 

 long, whose margins are not sharply defined. On both outer and inner 

 sides of the penultimate segment, near the flexor side, is a longitudinal 

 row of sabre-shaped or ensiform bristles of medium length. On the inner 

 distal margin of the same segment are also seen several finely pectinate 

 bristles. The terminal segment is noticeable for its considerable length 

 and comparatively stout form; its tip is beset with five slender spines 

 (Fig. 7). _ 



The genital aperture is bounded on each side by an arcuate, chitin- 

 ous ridge 225/Lt long, which is closely beset with bristles about 1351" long. 

 The penis-skeleton (Penisgeriist) is about 41 5M long and consists in the 

 main of two long chitinous arms, which meet together at their arcuate, 

 anterior ends, from which a common process is given off forw^ards. The 

 free end of this arm is markedly thickened. 



Locality: — Pond near Dechenes. 



Eylais marshalla Koen., n. sp. 

 Syn. Eylais extendens Koenike: Abh. Nat. Ver. Bremen, 1895, XIII 

 Bd., S. 171. 



