114 GEO. H. HORN, M. D. 



The mandibles are of irregular triangular form, thin and translucent, 

 convex above, concave beneath, the inner edge finely fimbriate, the apex 

 very acute and prolonged. 



The maxillae are bilobed, outer lobe longer with moderately long and 

 rather dense ciliae, inner lobe shorter, ciliate externally and with shorter 

 and stouter hairs internally. The palpi are four-jointed as shown in 

 the figure. 



The mentum is transverse slightly concave beneath, narrowed in front, 

 the hind angles prolonged in long slender processes over the gula. On 

 the front of the mentum is an accessory piece. Ligula concealed behind 

 the mentum, the paraglossae prominent, alate, united on the median line 

 and finely fimbriate along their margins. The palpi are short, three- 

 jointed, the penultimate joint longer than the others, the basal support 

 slightly projecting beyond the mentum causing the palpi to appear 

 four-jointed. 



The head is provided at the posterior angles, under the lateral margin 

 with an oval translucent eye spot recalling a similar structure in Adelops 

 or in some Anophthalmi. 



The presternum moderately separates the anterior coxae and is fimbriate 

 at tip, the coxal cavities open behind. 



The plate gives in sufficient detail the under side of the body. 



The legs are not long. The anterior and middle coxae have a distinct 

 trochantin. Anterior tibiae slightly broader to tip, ciliate at the outer 

 angle, the tarsi dilated in both sexes but more widely in the male, the 

 fourth joint bilobed. Middle tibiae stout, ciliate and finely spinulose 

 externally, the tarsi dilated but less widely than on the anterior legs, the 

 fourth joint less distinctly bilobed. Posterior tibiae slender, ciliate and 

 spinulose, tarsi slender, first joint nearly as long as the next two, the 

 fourth joint slender. Tibial spurs all distinct. 



The relationship of Leptinus has already been discussed by Dr. LeConte 

 and will not be repeated here, and as fuller details of its structure will be 

 given in a forthcoming work, merely enough is given here to render the 

 accompanying plate intelligible. 



Details of structure are illustrated on Plate V. 



PL,ATYPSYL,L,A Ritsema. 

 This genus is founded on a curious parasite discovered on the Ameri- 

 can Beaver in captivity in the Zoological Gardens at Amsterdam. By 

 Mr. Ritsema it was placed in a relationship not very remote from the 

 true fleas. Prof. Westwood who described the insect about one month 

 later believed it typical of a new order which he named Achreioptera . 



