( 166 ) 



Modified Segments. — The eighth tcrgitc bears fonr bristles at the dorsal edge 

 from the stigma to the apex, the first being thin and short and the fourth standing 

 close underneath the third. There fire, moreover, about five more bristles further 

 down, nnd a vertical row of three near the ventral margin. The eighth sternite is 

 long, rod-like, and curved, bearing one bristle at the apex on each side (PI. VI. 

 fig. 11, viii. St.). The process of the clasjier (PI. VI. fig. 11, r) is broad, being 

 ronnded at the apex, nearly reaching to the tip of the finger and bearing at the 

 distal side a pair of long bristles halfway down towards the insertion of the finger. 

 The latter is long, being almost straight on the proximal side, but evenly ronnded 

 on the distal side. It bears five bristles at the distal side, of which the ventral 

 one is (he stoutest and the uppermost the longest (PI. VI. fig. 11, f). The 

 manubrium (ji) is nearly straight at the apex and obtuse, though its apical fifth is 

 rather narrower than in most species. The outline of the ninth sternite cannot be 

 made out from the single specimen at our disposal. It bears a patch of hairs before 

 the middle. 



Length : c?, 2-4 mm. 



We have 1 c? from Horse Creek, Upper Columbia Valley, B. C, October 13tli, 

 1903, from Peromijscm canadensis, collected by Mr. G. F. Dijipie. 



10. Ceratophyllus aeger spec. nov. (PI. VI. figs. 5, 7, 9). 



This insect is very closely allied to C. wickhami Baker, being perhaps only a 

 geograjihical form of it. It is distinguished in both sexes by there being eight or 

 nine hairs on the outerside of the hindtibia, instead of the five or six (seldom seven) 

 found in wickhami. The hindtarsus is shorter than in that species, especially the 

 fourth and fifth segments. The second hindtarsal segment bears three pairs of 

 bristles on the posterior side, including the apical bristles, the first pair standing far 

 before the middle. The measurements of tlie mid- and hiudtarsi of tcickliaiiti and 

 the new species are as follows : — • 



In the male oi aeger the eighth tergite bears two bristles near the ventral edge 

 instead of three. The eighth sternite is small in both species. It is without 

 bristles, and is more reduced in ai'ger than in n-irhhami. The internal vertical 

 process is shorter, and the long membraneous apical lobe (which bears minute hairs) 

 is narrower thiin in Baker's 'species. The process of the clasper is much broader 

 than in «'ie/r'/OTw/ [(compare PI. VI. fig. o with fig. (i). The finger is narrow at the 



