4 IVAR TRAGARDH 
The pseudostigmata (fig. 4) are oval and hidden underneath the edge of 
the proterosoma; 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 Phthiracaridee. 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 Ortbotritia faroensts 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 Oribatide in 1910, f.i. in Orzbata, Notaspis, Ceratoppia, 
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 Phthiracaride. 
Maxille (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 IgI0, 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 
