studies oil iiuiriiu; Oslracods -'•• 



to this 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 Philotnedes 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 imjointed. In the C y p r i d i n i d s and the 

 Polycopids the exopodite is situated at the typical place for that organ, dorso-distally- 

 laterally on the basale, in the Halocyprids it is in most cases or perhaps always displaced 

 somewhat medially. In the other groups, Cyprids, Darwinulids, Nesideids, 

 C y t h e r i d s and Cytherellids, 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 Cyprids, 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 fact that in the family Polycopidue the mandi- 

 bular exopodite appears in two different types. One of these tjrpes resembles rather closely 

 the one that is characteristic of the C y p r i d i u i d s; cf. G. \V. MOLLBR, 1894, pi. 7, fig. 7 ; 

 the other shows a close agreement with the vibratory plate of the Cyprids, etc. ; cf . G. \\. 

 MOller 1894, pi. 7, fig. 39. That this process on the mandible of the Polycopids really 

 corresponds to the exopodite is shown with all desirable distinctness first by its position and 

 secondly by a comparison between the mandible and the maxiUa in this family; cf. figs, in pi. 7, 

 G. W. MOLLER, 1894. 



The following are the reasons why tliis opinion has nevertheless not been accepted 

 in this work: 



It is true that all Cyprids, Darwinulids, Nesideids, Cytherids and 

 Cytherellids are, apart fi'ora the vibratory plate, 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 Halocyprids, 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 half-way up the joint. In the genus ConcJioecia 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 verruci- 

 form appendage could be observed in these genera. In the genus Tliaumatocypris there is at 

 the corresponding place, according to G. W. MUller's work of 1906 a, ])1. VI, fig. 7, a curious 



* This is presumal)ly also tho case in tlie gomis Aichiconchoccia. hut nn a< count of lack of material I cannot 

 give a definite opinion as to this. 



