THE APPENDAGES, THEIR RELATIONSHIP AND FUNCTION 313 



the whole appendage. It is broad, being flattened laterally in relation to the animal. On its anterior 

 border it bears a series of four long setae, which extend forward to the region of the outer setae of the 

 basis of the mandible. On the posterior margin there are three long setae which extend ventrally and 

 backwards outside the maxillary endites. The anterior edge and inner face bear three further setae, 

 which extend medially beneath the endites, together with a single seta arising from the inner face of 

 the basis. The terminal article is cylindrical, tapering only slightly towards its apex. In Conchoecia 

 antipoda its length is only slightly greater than the width of the previous article and it is normally 

 directed backwards at right angles to the axis of the palp. At its apex it bears a group of five setae. 

 Two of these are stout claws, of which one is about two-thirds the length of the other. Two other 

 setae are more slender, but claw-like, and of about the same length as the shorter main claw. The fifth 

 seta is very slender and about the same length as the longest claw. All of these curve forwards. 

 Muller (1894) stated that the endopod is so bent inwards that it lies nearly parallel to the endites of 

 the stem. It is true that the palp may take up this position, but it may also slope outwards to some 

 extent. Besides this, some antero-posterior movement can take place. The end-article seems only 

 capable of movement through a dorso-ventral arc, relative to the preceding article. The extent of this 

 movement is from a position in line with the rest of the limb to one pointing posteriorly almost at 

 right angles to it. Rotation of the protopod about its axis results in movement of the apical article 

 of the palp through a horizontal arc, so that its total field of action is fairly large. It can be extended 

 backwards with its claws interlacing with those of the maxilla, or extended forwards with them lying 

 over or between the gnathobases of the mandibular basis. It does not, however, seem that the claws 

 can be extended into the oral atrium, or folded inwards sufficiently to reach the endites of the protopod 



of the limb. 



It has been pointed out above, that the maxillulary palps have anteriorly curved apical claws and 

 their movement must be mainly through a horizontal arc. In fact it seems probable that their main 

 function must be to pass food material forward on to the gnathobases of the mandibular bases. The 

 maxillulary endites are well developed, but their armature is very much less powerful than that found 

 in the cypridinids where they are used for mastication of the food (Graham Cannon, 1933). It would 

 seem that in halocyprids they have little masticatory function. The direction in which their few spines 

 and setae point and their range of movement would indicate that the distal endites probably serve to 

 grip food in the mid-line and to transfer it from the gnathobases of the mandibular bases to the region 

 of the incisor edges of the mandibular coxae in the oral atrium. Similarly it seems likely that the 

 proximal endites push food forward on to the molar surfaces of the mandibular coxae and aid transport 

 of food into the mouth. 



Maxillae (Figs. 7, 10 & 11) 

 The maxillae are biramous with one ramus jointed and pediform, the other unjointed. The protopod 

 bears a well-developed epipod. 



There has in the past been some variance of opinion regarding which pair of appendages the fifth 

 pair of limbs of many ostracods represent. Graham Cannon (1925, 1926) has shown quite clearly that, 

 on the basis of the segmental excretory organs, in Cypridopsis vidua ( = Pionocypris vidua), they are 

 the maxillae. There is no reason to doubt that they represent the same pair of appendages in the 

 Halocyprididae. Besides this, however, there are almost as many opinions regarding the homologies 

 of the parts of the limb as there have been workers on the group. This is too extensive a topic to 

 consider here in detail. On the basis of the musculature and segmentation of the appendage, it would 

 appear that Skogsberg's view (1920) is reasonable. This view is: that the shaft extending ventrally 

 from the body of the animal (Figs. 7, 11) is the protopod; the inwardly directed distal 'endite' with 



