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Tn arriving at a certain identification of species at least as much trouble is caused by
the faet that too few characters have been taken into considération as by the lack of exactness
in preceding writers. A very large number of species, for instance, have only the characters
of the shell described. G. S. BUADY wrote, 1868 a p. 112: „By far the greater number of
Ostracoda at present known have been described from fossil specimens“; in the original
descriptions of these forms of course onlv the characters of the shell have been taken into considération.
A rather large number of these species have been since identified with living forms, but the
extent of the descriptions has not, however, been increased. G. S. BRADY himself has afterwards
very much increased the number of species that are only described by shell characters. A good
illustration of this undesirable state of affairs is also shown by the fact that in G. W. MÜLLER’s
large monograph on the Ostracods of the Bay of Naples, undoubtedly the foremost
work on this group of animais that vre possess, the author has only included characters taken
from the shell and the penis in the diagnoses of the great majority of the very numerous species
belonging to the family Cytheridae. The appendages, their number of joints, bristles, etc. are,
on the other hancl, as a rule not included at all in these diagnoses. To this may be added that
in almost all cases only a few appendages of these forms are reproduced. A number of this
author’s later Works, e. g. that of 1908, are even worse in this respect.
The situation in most groups is really such at the present time that if the locality of the
find is situated near the type locality of a previously described species one may venture
perhaps — though with hésitation — to establish identity, but if the two localities are situated
in regions that from the point of the view of their fauna are different one is inclined not to
make an identification, although there are no differences according to the diagnosis of the
species and the figures. Only a few descriptions of species that have been carried out so far
can really be considered so complete and certain that merely on the basis of a comparison
with them it is possible to distinguish minor systematic units, e. g. geographica! sub-species.
A natural conséquence of the above-described uncertaintv and incompleteness of the
descriptions of species is that the diagnoses of genera and families in this group of animais are
also characterized by great uncertainty and incompleteness. Even the diagnoses of genera and
families foimd in G. W. MÜLLER’s above-mentioned large monograph, 1894, are anything but
satisfactory. Only a comparatively few characters are included in these. This is of course
due to some extent to the faet that this investigator only had an opportunity of personallv
investigating in detail a rather limited number of species in each group, but on the other hand
his intentions do not seem to have extended very far. A single typical example may be
given: In the diagnosis of the family Nesideidae we read concerning the mandible, p. 265:
„Die Mandibel mit kräftigem Kaufortsatz, der 4 längere, 3 spitzige und einige kleinere,
einfache Zähne trägt, zwischen den Zähnen entspringen Borsten; Taster deutlich viergliedrig,
das letzte Glied mit starker Klaue; die Athemplatte mit wenigen (3) Strahlen, von denen einer
außerordentlich lang ist.“ In the diagnoses of the two genera of this family Nesidea,
p. 267, and Bythocypris, p. 275, this limb is not mentioned at all. The same thing is also
true with regard to the diagnoses of the ten species belonging to the former genus and with
regard to the diagnosis of the only species of the genus Bythocypris. This limb is only repro-
I ncompleteness of the
diagnoses of genera
and families.
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