TWO SPECIES OF PARASITIC MITES. 



333 



the outline of the body, or rather circle round the anus, which, in 

 this species, is placed almost in the centre of the back. As the 

 folds approach nearer the anus they become less and less continuous, 

 becoming first rows of rounded papillae, and then disappearing 

 almost altogether. Towards the anterior end of the dorsal surface 

 and near the median line are two short spines, one on each side ; 

 and a somewhat shorter one is present on each side near the lateral 

 margin. On each side of the anus there are two curved rows of 

 short, blunt bristles, forming a kind of double arch over it, and 

 made up, the outer one of four, the inner one of two bristles on 

 each side. These point in a general way backwards and inwards 

 towards the anal opening. Anal bristles on the posterior end of the 

 body are entirely wanting. 



The dorsal position of the anus is very peculiar, and it was this 

 that suggested the name " notoedres," which Bourguinon and 

 ■Delafond applied to this species. It is strange that the peculiarity 

 should have escaped the notice of earlier observers, as it is very 

 well-marked. Fiirstenberg, who has given some very fine figures of 

 this species, cakes no notice of the dorsal opening, but indicates an 

 opening on the ventral surface where none exists. 



At the anterior end of the body is situated the rosti'um, composed 

 of the following parts : A pair of biting three-jointed mandibles, 

 the third joint springing from the side of the second and growing 

 out to an equal length with it, the opposed edges being furnished 

 with blunt serrations, thus forming strong nippers on each side of 

 the mouth. Below these are the immovably united maxillae with 

 their three-jointed palps, which extend forward parallel with the 

 mandibles. A thin fold of the integument surrounds the whole, 

 enclosing it in a kind of sac open in front, called by Robin the 

 camerostomum. Viewed from the dorsal surface a portion only of 

 the rostrum is seen, as it is partially covered by a fold of the skin 

 which projects over it. 



The body is provided with four pairs of five-jointed legs, two 

 anterior and two posterior, the anterior arising from the antero- 

 lateral margins of the body, the posterior from the hinder portion of 

 the ventral surface. The first four joints of these legs are surrounded 

 and strengthened by rings of chitin of a more or less irregular 

 shape, and are armed along their sides with bristles whose positions 

 are constant in the same species. The fifth joint is covered with a 



