TRACHEART^. 219 



Argas, Lat. — Rhynchoprion, Herm. 



Distinguished from Ixodes by the inferior situation of the mouth, 

 and by the palpi which do not encase the sucker, have a conical 

 form, and are composed of four joints, and not of three, as in the 

 preceding genus. 



Argas reflexus; Ixodes reflexus, Fab.; Lat. Gen. Crust, et In- 

 sect., I, vi, 3, Herm. Mem. Apt. IV, 10, U. Pale yellow, with 

 dark blood-coloured, or obscure and anastomosing lines. — On 

 Pigeons. 



Argas persicus; Malleli de Mianeh. This species, described 

 by travellers under the name of Punaise venimeuse de Miana, 

 with other Ixodes, constitutes the subject of some curious ob- 

 servations published by M. Gotthef Fischer de Waldheim. 

 Others again — Hydrachnell^e, Lat. — have also eight legs, but they 

 are ciliated and adapted to natation. 



They form the Genus Hydrachna of Muller(l) or that of Athax 

 Fab., and are wholly aquatic. Their body is generally oval or nearly 

 globular, and very soft. That of some males is narrowed posteriorly, 

 so as to resemble a kind of tail, their genital organs being placed at 

 its extremity; in the female, they are on the inferior surface of the 

 abdomen. The number of eyes varies from two to four, or, accord- 

 ing to Miiller, even to six. 



The mouth of those species, I have been able to study, offered the 

 three following modifications, which have served as a base to three 

 generic divisions, but to which it is almost impossible to refer all 

 Miiller's species of Hydrachnae, that naturalist not having described 

 them with sufficient minuteness. 



Eylais, Lat. 

 Chelicerse terminated by a movable hook(2). 



Htdrachna, Lat. 



The mouth composed of laminse, forming a projecting sucker; a 

 movable appendage under the extremity of the palpi(3). 



De Geer, lb., XXVlf, 9, 13. See the genus Ixodes of Fabricius, and the work of 

 Leach on the apterous Insects of Linnxus — Trans. Lin. Soc, XI. 



(1) Hydrachna, Herm. 



(2) Atax extendens. Fab.; MiilL, IX, 4. 



(3) Max geographicus, Fab.; Miill., "VIII, 3, 5; At. globator. Fab.; Miill-, IX, 1- 



