ACARINA FROM THE JUAN FERNANDEZ ISLANDS 607 
Upper jaw with numerous teeth, the largest one being inserted opposite 
the median tooth of lower jaw; in front of this the edge is excavated, with 4 
small teeth; pilus dentarius being inserted on a level with the last of these; 
further backwards a small tooth, then a thin blade, then a rounded incision 
and then a small, blunt tooth. 
Loc.: Juan Fernandez, Masatierra, among dry leaves. 
20. Sejus insulanus n. sp. — Figs. 118—120. 
Amongst the dry leaves mentioned above (p. 587) there was also a specimen 
of Sejus, a female, much shrunken and deformed but nevertheless well enough 
preserved to be described. Hitherto only two species of Sejws (taken in modern 
sense) seem to be recorded from America, S. americanus BANKS and S. pari- 
cornis BERLESE from Buenos Aires, previously wrongly interpreted as S. acan- 
thurus BERL. (comp. BERLESE: Centuria seconda di Acari nuovi. Redia. Vol. 
XII. 1916, p. 150). 
The present species is easily recognized by the short projections at the 
posterior margin. In neither of the american species is the exceedingly re- 
markable shape of the sternal and genital shields described. It is, therefore, 
impossible to compare the present species with these. I must confine myself 
to the european species S. ¢ogatus K. of which I have material collected in 
Sweden. 
Length 660 », width 420 uw. 
The shape and structure of the dorsal shields I have not been able to 
see distinctly. There is a marginal shield which is very narrow as far as 
to the middle of the ventri-anal shield but widens further backwards towards 
the posterolateral angle. It bears 2—3 rows of short, cylindrical projections 
each bearing a stout, short pointed bristle, curved sharply backwards and 
slightly serrated. At the posterolateral angle there is a longer, conical pro- 
jection carrying a larger bristle and at the posterior margin there are two pairs 
of projections slightly larger than the lateral ones and carrying larger bristles 
curved towards the middle. 
Ventral side (fig. 119). The sternal and genital shields are of a very 
peculiar shape, quite unique amongst the Mesostigmata. It is, therefore, very 
deplorable that neither BERLESE nor BANKS have paid any attention to these 
structures. Already in 1912 I described them briefly in Sejus fogatus K. (I. c. 
fig. 29, 30, p. 19). 
As a matter of fact these shields and the number of hairs on them are 
so different from anything hitherto known amongst the Mesostigmata that one is 
at a loss how to interpret them. As a rule there are on the sternal and genital 
shields in the female in all 5 pairs of hairs, of which 4 pairs belong to the coxal 
plates of legs I—IV and one pair to the epigynial shield (compare TRAGARDH 
1912, figs. 21—24). In Sejus insulanus and S. togatus, on the other hand, we 
find in the space between the coxz in all 7 pairs of hairs, of which 4 pairs 
are placed far forward between coxz II, and 3 pairs along the sides of the 
epigynial shield. 
