100 



TAGE SKOGSBBRG 



AtaxiUa. 



Fifth linib. 



Sixth limb. 



eventh limb. 



Brush-shaped organ. 



for Podocirpa tliiii\ to that of C y p i- i d i ii i <1 s and I* o 1 y c o |) i <1 s. — In liis work of 1912 

 G. \V. Mt'LLlili does not mention this limb in the diagnosis of Myodocopa, a fact that seems to 

 indicate that he has arrived at the same opinion about the classificatory vahie 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 inclined to believe from G. W. MOller's 

 statements. In Pohjcopidue, especially in a number of forms belonging to this family, we find 

 a maxilla of so simple a t>^e that from it we can quite naturally derive the types found in othci- 

 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 joiiits: the number of joints varies, however, somewhat, both in 

 Myodocopa and Podocopa. The most important difference according to G. W. MUller 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. MULLER 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 very- 

 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. MOLler, 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 find 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 C y t h e r e 1 1 i d s. 



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 tj'pe in Podocopa. In the males of the C y t h e r e 1 1 i d s we find a 

 type that differs very much from both Halocyprids, Cypridinids and other 

 Ostracods. G. W. Muller considers this limb of the Halocyprids to be of a 

 primitive t\'pe. 



Seventh limb: — This appendage is absent in both Polycopidae and CythereUidae. 

 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 agree- 

 ment with Podocopa than with the Cypridinids. 



Brush-shaped organ: — This organ is foimd both in Myodocopa and Podocopa. 

 It is presumably of a comparatively slight classificatory value as it probably existed, as 

 G. W. MilLLER has pointed out, even in the P r o t o s t r a c o d s. 



