GENUS CTENOPSYLLA 457 



antipygidial bristles on each side. No comb of minute teeth on the 

 inner side of the hind coxa. The last joint of the hind tarsus has five 

 pairs of lateral spines, all in a line or only the last pair slightly dislocated. 



GENUS PYGIOPSYLLA, ROTHSCHILD 



This genus is distinguished from Ceratophyllus by the marked convexity 

 of the pygidium. Fifteen species are known, mostly from the tropics. 

 Of these hilli, Rothsch., and rainbowi, Rothsch., have been found on 

 Mus rattus, though their normal host appears to be Mus assimilis, on 

 which they occur, together with P. gravis, in Australia. 



GENUS CHIASTOPSYLLA, ROTHSCHILD 



This genus includes three South African species, one of which, Ch. rossi, 

 has been taken on a rat. The genus is distinguished from Ceratophyllus 

 by the presence of two spines at the genal edge of the head, one lying 

 on top of the other, and by the presence of one antipygidial bristle 

 on each side. The hind coxa has a comb of spines on the inside, and 

 the mid and hind femora bear no lateral rows of bristles. 



GENUS NEOPSYLLA, WAGNER 



One species, N. bidentatiformis, Wagn., has been found on a rat in 

 Russia. 



GENUS CTENOPTHALMUS, KOLENATI 



This is also a large genus, the species of which are widety distributed. 

 In addition to the structural features given in the key, the genus is 

 distinguished as follows. The genal comb consists of fewer teeth than 

 in Ctenocephaltis. Midway between the palpi and the antennal groove 

 there is a distinct frontal tubercle situated in a groove. There are three 

 antipygidial bristles on each side. Ct. agyrtes is common on field mice 

 in England, and is found also on Mus norwegicus, when captured in the 

 open country. It has three teeth in the genal comb, and sixteen on the 

 pronotum. Ct. assimilis occurs on field mice in Central Europe, and 

 has also been found on rats. It has three teeth on the genal comb and 

 sixteen on the pronotal one. 



GENUS CTENOPSYLLA, KOLENATI 



This genus presents such marked characteristics that Baker has pro- 

 posed to place it in a separate family, the Ctenopsyllidae. The most 

 striking feature is the shape of the head, which is pointed anteriorly, the 

 angle being situated not far in front of the antennal groove. As a result 

 of this retroflection of the anterior and dorsal part of the head the genae 

 are almost vertical, and the antennal groove almost horizontal instead of 

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