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Maxilla.
Fifih Umh.
Sixth Limb.
Seventh limb.
Brush-shaped organ.
for Podocopa than to that of C v p r i d i n i d s and P o 1 y c o p i d s. — ln his work oi 1912
G. W. Müller does not mention this limb in the diagnosis of Myodocopa. a faet that seenis to
indicate that he has arrived at the same opinion about the classificatory value of this organ as
that adopted in the present treatise.
Maxilla: — With regard to this limb it may be said that it shows less difference
in Myodocopa and Podocopa than one would be inelined to believe from G. W. MÜLLER’s
statements. In Polycopidae, especially in a number of forms belonging to this family, we tind
a maxilla of so simple a type that from it we can quite naturally dérivé the types found in other
families. In most of the forms belonging both to Myodocopa and Podocopa the protopodite is
armed with three endites, in most cases powerful (in the Halocyprids two of these are,
however, almost completely joined). In almost all recent Ostracods the endopodite of
this limb has two or three joints: the number of joints varies, however, somewhat, both in
Myodocopa and Podocopa. The most important difference according to G. W. Müller would
undoubtedly be that in Podocopa the exopodite is developed as a vibratory plate, while in
Myodocopa this limb has no such organ. In this matter G. W. MÜLLER is, however, probably
quite mistaken; see p. 34 above.
Fifth limb: — As has been shown on p. 85 above, this appendage appears in very
different types in the recent Ostracods. The type found in the Halocyprids differs ven’
much from both the Cypridinids and the Polycopids, and has a striking
resem-blance, on the other hand, to the fundamental type in Podocopa. We must note, however,
that, according to G. W. Müller, the Halocyprids are to be regarded as primitive
with regard to this limb, an assumption which, although not at all proved, cannot, as we
have seen above, by any means be considered impossible. The Myodocopa would be characterized
by a powerful vibratory plate on this limb. This character is, however, of slight significance.
In the first place the vibratory plate is of rather moderate size in the Halocyprids;
secondly we also tind a rather powerful vibratory plate on this limb in forms belonging to
Podocopa, e. g. a few C y p r i d s, all N e s i d e i d s and Cytherellids.
Sixth limb:— This limb is absent in Polycopidae and apparently also in the
females of the genus Cytherella. In Halocyprids and Cypridinids it appears in
very different types; the type found in the former group shows a far-reaching agreement
with the fundamental type in Podocopa. In the males of the Cythereii i d s we find a
type that differs very much from both Halocyprids, Cypridinids and other
Ostracods. G. W. Müller considers this limb of the Halocyprids to be of a
primitive type.
Seventh limb: —- This appendage is absent in both Polycopidae and Cytherellidae.
In other forms it varies fairly considerably, but it may also be said of this limb — though
with a certain amount of reserve — that in the Halocyprids it shows a greater
agreement with Podocopa than with the Cypridinids.
Brush-shaped organ: — This organ is found both in Myodocopa and Podocopa.
It is presumably of a comparatively slight classificatory value as it probably existed, as
G. W. Müller has pointed out, even in the P r o t o s t r a c o d s.
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