60
THE ESSEX NATURALIST.
In the case of the Hydrachnids there are one or two species
which have been found in the sea (Mediterranean and Atlantic)
belonging to the genera Nautarachna and Pontarachna, but
none has yet been recorded as found round our own coasts. In
the year 1917 a paper was read before this Club on all the known
fresh-water mites found in Epping Forest. This was published
in the Essex Naturalist (vol. xviii., pp. 96-105), and although
a number of collections taken in the. Forest have been examined
since that date, there have been no new species to record.
As regards the Halacarids the position is somewhat different.
Although typically marine mites, different species are con-
stantly being recorded as found in fresh water. Dr. Walter,
of Basle, has recorded quite a number of these small mites,
and very small indeed some of them are, less than a third of a
mm. or l/75th inch in some cases. Very little work has been
done with the Halacaridae in this country. In Science Gossip
for 1899, p. 293, there is a short paper by Mr. R. Macer1 on an
Halacarid found by him in fresh water in the canal at Wey-
bridge, which is too far from the sea to have been at all brackish.
This mite was recorded under the name of Raphignathus falcatus
Hodge. On reference to Hodge's original paper- in the Tyneside
Naturalist, vol. v., part iv., 1863, p. 303 (plate xvi., fig. 6) I find
that it was first described under the name of Leptognathus
falcatus. G. S. Brady,3 who also figures the same mite in P. Zool.
Soc, 1875, p. 307 (Plate 42, fig. 7), and calls it Raphignathus
falcatus, Hodge. But Lohmann in Das Tierreich Lief. 13, 1901, has
placed it in the genus Trouessartella, Lohm., and that no doubt
is its proper place. In Hodge's figure the median eye is very
conspicuous, as it is in Mr. Macer's specimen. But in Brady's
figure the median eye is not shown. Lohmann, however, says
they are both intended for the same mite. Another curious
point about the median eye is that Lohmann himself has figured
this mite in the Zool. Jahrb. for 1888 as L. marinus, but has
omitted the eye !
About the time Mr. Macer's paper was published, Mr. Bostock
of Staffordshire, a well-known worker with Mr. Michael on mites,
wrote to me saying he also had found the same species in fresh
water.
1 "Sea water Mite found in Freshwater."
2 "On some undescribed Marine Acari."
3 "A Review of the British Marine Mites."