554 ivAR tragArdh 



The pseudostigmata (fig. 4) are oval and hidden underneath the edge of 

 the proterosoina; they are fairly deep, funnel-shaped, with the walls provided 

 with septa. The pseudostigmatic organs have long, slender, s-shaped stalks. 

 The heads are rather peculiar. Either they are so extremely fragile, that they 

 break off, or the heads are truncated, with uneven edges. At all events I have 

 not found any specimens with heads shaped in any other way than what fig. 4 

 shows. 



Mouthparts (figs. 3, 5). The palps. As pointed out by the author 

 (1930) there seems to be some uncertainty as to the exact number of 

 joints in the Phthiracarid?e. Doubtless Berlese was in error when he deline- 

 ated the terminal joint as consisting of two joints. In my opinion there are 

 only three free joints. It is true that at the base of the first joint there is a 

 ridge which may possibly be interpreted as indicating the rest of a basal joint 

 fused with the maxilla. But as long as no forms have been found on which 

 this retrogressive development may be traced it is just as easy to consider this 

 ridge as a mean of strengthening the support of the muscles moving the palps. 

 As in Oribotritia faroensis Selln. (1930, fig. 80) there is a thin horizontal 

 blade, covering the base of the ist free joint. The ist joint is very long, 

 longer than the 2nd and 3rd together and more than twice as long as high; 

 the joint is bent a little downwards in the middle and has two hairs a little 

 in front of the middle, one on the ventral (exterior) side, twice as long as the 

 other one which is inserted submarginally on the inner (dorsal) side. 2nd joint 

 tapering gradually forward, with two hairs, one long dorsal near the anterior 

 margin and one shorter in the middle of the ventral (exterior) side; 3rd joint 

 longer than the 2nd, cylindrical but rounded at the top; it carries three straight 

 terminal bristles, one curved, subterminal dorsal bristle, one dorsal hair a little 

 in front of the middle, another opposite it ventrally and on a line between 

 them one shorter hair externally. 



Mandibles (fig. 3) large, rounded posteriorly, with finely punctured cu- 

 ticle. Digitus fixus with two hairs, one larger, slightly hairy, on the dorsal 

 margin, exactly in the middle, the other smaller submarginally on the exterior 

 side, a little behind the cutting edge of the chela. Chela with 3—4 strong 

 teeth. 



On the inner (median) side of the mandibles there is a remarkable finger- 

 shaped, very thin-walled appendage attached behind the base of the digitus 

 mobilis and projecting forwards until the cutting edge of the chela. This ap- 

 pendage is evidently homologuous with that which I discovered and described 

 in so many genera of Oribatidae in 1910, f. i. in Oribata, Notaspis, Ceratoppiay 

 Tectocepheus and Nothrus and which I interpreted as a sense organ. At that time 

 I failed, however, to detect it in Hoploderma, but as the present investigations 

 show, it is also present in the Phthiracaridce . 



Maxillae (fig. 5) of the typical shape; they are posteriorly projecting as 

 very sharp angles, and from the exterior angle there projects straight forwards 

 a very narrow, pointed bristle almost exactly as in Phthiracarus borealis Trag. 

 (comp. TragArdh 1910, fig. 331, p. 548). The exterior edge is almost straight, 

 with a short, transversal incision in the middle. The anterior edge with the 

 usual blunt teeth. At the base of the palp there is a small hair, and about 



