■ Studies on iiiariiu; Oslracods 7 



In arriving at a certain identification of species at least as much trouble is caused by 

 the fact that too few characters have been taken into consideration 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. Brady wrote, 1868 a p. 112: ,,By far the greater number of 

 Ostracoda at present known have been described from fossil specimens"; in the original descrip- 

 tions of these forms of course only the characters of the shell have been taken into consideration. 

 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 imdesirable state of affairs is also shown by the fact that in G. W. MCl.LER's 

 large monograph on the s t r a c o d s of the Bay of Naples, undoubtedly the foremost 

 work on this group of animals that we 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 hand, 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 hesitation — 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. geographical sub-species. 



A natural consequence of the above-described uncertainty and incompleteness of the incompleteness of ihe 

 descriptions of species is that the diagnoses of genera and families in this group of animals are ' '"""nd^families"^'^" 

 also characterized by great tmcertainty and incompleteness. Even the diagnoses of genera and 

 families found in G. W. MOller'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 fact that this investigator only had an opportunity of personally 

 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 t}qDical example may be 

 given: In the diagnosis of the family Nesideidae we read concerning the mandible, p. 265: 

 ,,Die Mandibel mit kriiftigem Kaufortsatz, der 4 langere, 3 spitzige und einigc kleinere, 

 einfache Zahne triigt, zwischen den Ziihnen entspringen Borsten; Taster deutlich viergliedrig, 

 das letzte Glied mit starker Klaue; die Athemplatte mit wenigen (3) Strahlen, von denen einer 

 auBerordentlich 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 rcpro- 



