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to tilis last-mentioned group this limb may even be without the slightest trace of endites, as,
for instance, in the females of the genus Sarsiella. (For the endites on this limb in the males
of the genus Philomedes see the description of this genus in the present work.) The endopodite
is in most cases well developed and has well developed joints. The exopodite, on the other
hand, is always more or less reduced and is unjointed. In the Cypridinids and the
P o 1 y c o p i d s the exopodite is situated at the typical place for that organ,
dorso-distally-laterally on the basale, in the H a 1 o c y p r i d s it is in most cases or perhaps always displaced
somewhat medially. In the other groups, C y p r i d s, Darwinulids, N e s i d e i d s,
C y t h e r i d s and C y t h e r e 11 i d s, on the other hand, it is very much displaced proximally ;
in most cases it is situated near the proximal-lateral boundary of the basale. In most of the
last-mentioned groups it is used for respiratory purposes, it has been developed as a
vibratory plate.
The only point in the explanation given above as to which there seems to be the
possibility of any justifiable doubt is whether the organ that has been explained as an
exopodite in the C y p r i d s, Darwinulids, Nesideids, Cytherids and
Cytherellids is really homologous with the exopodite. This has been generally assumed
by preceding authors, but they have not given any reasons for this view of theirs.
This view seems to be supported by the faet that in the family Polycopidae the
mandibular exopodite appears in two different types. One of these types resembles rather closely
the one that is characteristic of the Cypridinids; cf. G. W. MÜLLER, 1894, pi. 7, fig. 7;
the other shows a close agreement with the vibratory plate of the C y p r i d s, etc.; cf. G. W.
MÜLLER 1894, pi. 7, fig. 39. That this process on the mandible of the P o 1 y c o p i d s really
corresponds to the exopodite is shown with all desirable distinetness first by its position and
secondly by a comparison between the mandible and the maxilla in this family; cf. figs. in pi. 7,
G. W. Müller, 1894.
The following are the reasons why this opinion has nevertheless not been accepted
in this work:
It is true that all C y p r i d s, Darwinulids, Nesideids, Cytherids and
Cytherellids are, apart from the vibratory piate, quite without any appendage on the
mandible that could be interpreted as an exopodite, and that in those forms of the C y p r
i-d i n i d s and Polycopids that are furnished with a typical exopodite on the mandible
there is no trace at all of any epipodial appendage on this limb. There is, however, one group,
the H a 1 o c y p r i d s, in which the second protopodite joint of this limb sometimes has two
appendages, one situated disto-dorsally, somewhat medially, the other proximo-medially, at
or somewhat above a point lialf-way up the joint. In the genus Conclioecia the former
appendage is represented by a small, verruciform process with a plumous bristle; in the
genera Halocypris and Euconchoecia * only by a plumous bristle, no traces of the
verruciform appendage could be observed in these genera. In the genus T/iaumatocypris there is at
the corresponding place, according to G. W. MÜLLER’s work of 1906 a, pi. VI, fig. 7, a curious
* This is presumably also the case iu the genus Archiconchoccia, hut on account of lack of material I cannot
give a definite opinion as to this.
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