studies on murine Ostracods 559 



in the forms with two protopodite joints, is usually somewhat smaller than the part that corre- 

 sponds to the coxale and has disto-anteriorly remains of enditcs, which are armed with a few bristles. 

 Apart from these this joint is quite without bristles. The epipodial plate is elliptically 

 oblong, situated vertically on the part of the protopodite that has been assumed above to be 

 homologous with the coxale, and is joined to this throughout its length; along the posterior 

 edge it has a moderate number of marginal bristles, arranged in three groups which are in most 

 cases clearly distinct. These bristles are furnished along the greater part of their length with 

 moderately long, fine, stiff hairs, placed close together and arranged in the form of a feather. 

 The endopodite, which is moved by special muscles and projects rather far in between 

 the protopodite and the exopodite, is armed with a rather large number of bristles. The e x o- 

 p d i t e is rather thick proximaUy and grows rather rapidly and uniformly thinner distally. 

 Its end joint, armed with three bristles, is always very small. 



See p. 46 above for the difference between the ideas of previous writers as to the mor- 

 phological value of the various parts of this limb and the ideas about this problem that are 

 expressed in the description given above. 



Sixth limb: — This limb, too, is subject only to rather slight variation within 

 this group. In the females it seems to serve chiefly as a climbing organ, in the males often 

 as an auxiliary organ in swimming, but in some cases, in the males of the genera Archiconchoecia 

 and Halocypris, genera which show only rather slight or no dimorphism in this limb, it is, as 

 in the females, chiefly a climbing organ; on the other hand it never seems, either in males or 

 females, to be used in mastication or taking up food. It is situated on the side of the body, 

 just behind the fifth limb. It is always rather large and has well-developed musculature; it 

 is always stronger and larger in the male than in the female. It is constructed according to 

 the same type as the fifth limb, consisting of a voluminous, rather elongated, ventrally pointing 

 protopodite, which is sometimes more or less distinctly two-jointed, but in most cases unjointed, 

 and which is always somewhat shorter than the exopodite, a moderately large epipodial append- 

 age that is developed as a vibratory plate, a very short, unjointed endopodite (sometimes not 

 bounded off from the protopodite and then not possible to establish) and a four-jointed, 

 backward or backward-upward pointing exopodite, which is in most cases somewhat more 

 elongated in the males than in the females. Protopodite: This is of Cjuite the same 

 type as the one on the fifth limb; like the latter, it is closely joined to the body proximo- 

 medially, but it is quite without any trace of endites. The epipodial appendage has 

 about the same size, type and position as this organ on the fifth limb; it differs from this chiefly 

 by the number of the bristles. The endopodite projects somewhat farther in between 

 the protopodite and the exopodite than on the fifth limb; its muscles are very much reduced 

 or are even quite absent; it has only a very small number of bristles. As in the case of the preced- 

 ing limb the exopodite is rather thick proximaUy, and grows rather rapidly and uni- 

 formly thinner distally. Its end joint, armed with three bristles, is always small. 



For the differences in the ideas about the different parts of this limb held by previous 

 writers and those put forward in the [)resent work see p. 50 above, the chapter on the general 

 morphology of the limbs. 



