CRUSTACEANS 
Lynceidz, but that name is wanted elsewhere, so that the present family 
Is properly named Chydoride from the typical genus CAydorus established 
for this very species by Dr. Leach in 1816. It agrees with the Bos- 
minidz in having five or six pairs of feet equally spaced, but is distin- 
guished by having only three joints in both branches of the second 
antenne. There is also another peculiarity, not difficult to observe 
through the pellucid valves of various species. The intestine, which 
in the two preceding families may make a more or less serpentine bend, 
here goes the length, not exactly of tying itself into a knot, but of form- 
ing one complete convolution and half another. 
Within the compass of this same family two species were recorded 
in 1867 by Norman and Brady, as having been found by the latter author 
in Thirlmere. Already numerous genera had been carved out of the 
original Lynceus, but not all of these at that date commended themselves 
to the two writers just named as worthy of adoption. Consequently 
they called the specimens from Thirlmere respectively Lynceus guttatus, 
G. O. Sars, and L. exiguus, Lilljeborg.' According to the nomencla- 
ture now generally accepted the former will stand as A/ona guttata, 
Sars, and the latter as A/onel/a exigua (Lilljeborg). Both occur in Nor- 
way as well as in England, and in regard to the second Professor Sars 
makes the interesting comment that he had at one time confused it with 
A. excisa (Fischer), but had afterwards found these two little species 
to be easily distinguishable, when alive, even by the unassisted eye. 
Fischer’s species, he explains, swims with quite a smooth motion, where- 
as A. exigua gets along by jerks and rapid leaps.’ 
The Onychopoda possess but one family, the Polyphemidz, in 
which the genera are few, and of those few some are exclusively or 
almost exclusively marine. There are two freshwater genera, both of 
which are represented in Cumberland. These are Polyphemus, O. F. 
Miiller, and Bythctrephes, Leydig. 
According to Miss Pratt Polyphemus pediculus (Linn.) ‘was very 
rare in Bassenthwaite in April, but very abundant and universally dis- 
tributed at the surface and some little distance below the surface in June, 
with eggs, embryos and larve in all stages of development.’ In this 
remarkable family the feet project from the shell and assist the antenne 
in the function of swimming. The brood cavity is very large. So also 
is the eye, the ever-trembling eye, which is so striking a feature in many 
Cladocera. For Polyphemus Miiller effectively says that the head is all 
eye. 
In 1883 Conrad Beck, writing ‘On some new Cladocera of the 
English Lakes,’ makes the following remarks on Bythotrephes cederstrémi, 
Schédler :-— 
‘The anterior portion of the head is almost entirely occupied by 
the eye, a large pigment mass surrounded by a number of long trans- 
1 Nat. Hist. Trans. Northumberland, etc., vol. i. pp. 381, 385 (1867). 
2 Vid.-Selsk. Forhandl. Christiania, No. 1, (1899), p. 48. 
3 Ann, Nat, Hist., ser. 7, vol. ii. p. 472. 
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