324 DISCOVERY REPORTS 



1931, 1933) has pointed out that in the Cypridinidae there has been a backward shift in adaptation 

 of the limbs for this purpose. Here, instead of the mandibles, the maxillules and maxillae are the 

 main biting-mouth-parts. This is accompanied by a more posterior position of the mouth relative to 

 the appendages. Thus the mouth lies posteriorly to the mandibular coxae, the oral atrium being 

 bounded laterally by the maxillulae ; the paragnaths are not developed. In Conchoecia, however, like 

 the Podocopa, the mandibles are the main biting-mouth-parts, with the maxillulae playing only a 

 small part in the process and the maxillae not adapted at all for biting the food. In this genus the 

 mouth lies between the mandibular coxae, which also laterally bound the oral atrium, and the 

 paragnaths are well developed. The difference in adaptation of the appendages for feeding is correlated 

 with adaptation for walking. Thus in bottom-living cypridinids the mandibular palp is used for 

 walking and the mandible is no longer used for biting the food. The gnathobase is reduced and adapted 

 merely to assist transport of food into the mouth. The same pattern is retained in planktonic members 

 of the group, such as Gigantocypris (see Graham Cannon, 1940), or Cypridina (Macrocypridina) castanea 

 (see Graham Cannon, 1933) which is illustrated for comparison with Conchoecia in my Fig. 14. In 

 the Podocopa, on the other hand, it is the antennal endopod which is used for walking and this leaves 

 the mandible free for biting the food. Conchoecia does not walk at all and the mandible is free for 

 biting the food. The palp, though well developed, differs in structure from that of the Cypridinidae 

 and is used for capture of food. 



SUMMARY 



The functional interrelation of the appendages and their setae in Conchoecia borealis antipoda is 

 described. Apart from differences in secondary sexual characters, there is little difference in other 

 members of the genus Conchoecia. 



A new feature of the articulation of the mandible with the body has been found in the Halo- 

 cyprididae. A distally directed condyle on the distal apex of the coxa articulates in a skeletal socket 

 on the oral surface of the labrum. This with the usual dorsal condyle restricts movement of the coxa 

 to rocking about a vertical axis. 



The anterior dorsal extrinsic muscle of the mandibular coxa is inserted on a flange which extends 

 forward from the region of the dorsal condyle. This muscle thus serves to rotate the coxae outward 

 and separate the mandibular gnathobases. 



It has been confirmed that members of the genus Conchoecia are mainly predators on copepods. 

 The method of capture and mastication of such food is discussed. The gnathobase of the basis of the 

 mandible is probably concerned with reducing such food to a size that can be swallowed. 



It seems probable that Conchoecia species can also feed on fine material. This may be collected by 

 the secretion of the marginal glands of the carapace or by labral gland secretion. 



The appendages of Archiconchoecia, Euconchoecia and Halocypris are in general similar in structure 

 and arrangement to those of Conchoecia. Their mandibles have the same type of articulation. There 

 are, however, differences in the gnathobases of the mandibular coxae, which must result in functional 

 differences needing investigation. 



The differences in the gnathobases of the mandibular coxae of Halocypris globosa and H. brevirostris 

 are probably of sufficient significance to warrant inclusion of these species in separate genera, as 

 suggested by Claus. 



A redescription of Thaumatocypris echinata Miiller is necessary, in order to clarify its systematic 

 position. 



Conchoecia is compared with Cypridina. The functional pattern of the mandibles and more posterior 

 limbs of the former, as well as the position of the mouth, do not show the backward shift present in 

 Cypridinidae. 



