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Laguna @arine Laboratory 17 
SOME MARINE AND TERRESTRIAL ACARINA 
OF LAGUNA BEACH 
HARRY V. M. HALL 
During the summer we picked up quite a series of mites, many of 
them new species. From this material I describe the following mites 
which are mostly marine or littoral. Among them the Gamaside 
are represented by a species that is parasitic on the large beach 
amphipods, a Sareoptid was taken from one of the birds, the Trom- 
bidide are represented by a large red Rhyncolophid common on the 
dry sand of the upper beach, the Hydrachnids by a new marine 
species and the Halicaride by three new species. In the last two 
families good series were obtained but only by means of much towing 
and patient search. 
Seius orchestoideae n. sp. 
(Figure 96) 
Length without rostrum 641 micrm., 542 mierm.; width 410 micrm., 
320 micrm. Length of legs one and four about 520 micrm.; length of 
legs two and three about 400 micrm. Color of female light straw, 
that of male still lighter; smooth but not polished. Dorsal plate en- 
tire and covering whole dorsum. Shape ovoid, the anterior end some- 
what sharper (especially so in the male) and the posterior end 
rather flattened (also most marked in the male). Body broadest one- 
third of the way from the posterior end. The outline form above 
runs to the rounded anterior point without any shoulder-like bulge 
in either sex. Dorsal surface evenly convex. Mandibles greatly 
retractile (shown extended in the figure but can be drawn wholly 
within the body). Both arms of chele short, stout. The fixed arm 
with a terminal beak proximal to which is one other tooth; the 
movable arm has two teeth which fit between and proximal to those 
on the fixed arm. From the movable arm and pointing outward 
and forward is a cylindrical process slightly swollen at the end in 
the male but not so swollen in the female. This process is about 
the same diameter as one of the leg-spines measured at the base 
of such a spine. Coxe almost contiguous and legs long, without 
apophyses in either sex; all lees sparsely set with short, stout spines 
and terminated by short caruncles with claws on all legs. Dorsal 
surface with a few very heavy spines, over twice the diameter of 
those on the legs and placed as follows: (except for the first pair 
at anterior margin and close together, all these spines are directed 
