3 i8 DISCOVERY REPORTS 



posterior gape of the carapace, or it may be flexed forward to bring the furcal claws between the bases 

 of the appendages. In this latter position, the anterior claws extend between the endites of the maxil- 

 lules, with their apices almost in the oral atrium. There can be no doubt that these claws have a 

 cleaning function as is commonly the case in ostracods. 



Penis 



The structure of the penis of the halocyprids has been described by Skogsberg, but though his and 

 earlier descriptions make it difficult to understand the three-dimensional structure of the organ, this 

 is not in itself relevant to the present topic. It is, however, worthy of note that this extremely large 

 organ is unilateral and set well to the side of the animal. In this position, though it extends downwards 

 to the ventral margin of the carapace, or even beyond, it does not impede the movement of the limbs 

 and leaves a clear path for the flexure of the trunk and anterior extension of the caudal furca. 



FEEDING-MECHANISM 



Type of food 



Muller (1894, 1927) stated that the stomachs of halocyprids contained the remains of copepods. He 

 further stated that these have been trapped on the sticky shell, drawn in by the mandibular palps and 

 conveyed with the sticky secretion of the shell-glands into the mouth and stomach. Elofson (1941) 

 also found copepod remains in the stomachs of certain species of Conchoecia and I too have found such 

 copepod remains in the stomachs of numerous species. I have even seen a specimen of C. bispinosa, 

 which had a large part of the crushed but only slightly dismembered exoskeleton of a small copepod 

 in its stomach ; usually, however, the only identifiable remains are limbs, but it has not been previously 

 noted that these are usually derived from animals of a size equal to or greater than that of the ostracod. 

 It is difficult to understand how large prey could be trapped in a sticky secretion of the carapace, 

 unless this secretion was much more copious than would be indicated by the size and number of the 

 glands. In fact, the stout spines and claws present on the mandibles and maxillules, together with the 

 powerful gnathobases of the former, give the impression of a voracious predator. 



I have noticed that, whether or not there are any copepod remains in the stomach of a halocyprid, 

 there is usually a mass of fine material. This confirms Muller's observations (1894); but in addition 

 the material sometimes contains diatom remains, a fact not stated by Muller. The type of food con- 

 tained in the stomach bears little relation to the size of the animal. Thus, some stomachs of the large 

 C. valdiviae have been found to contain nothing but fine detritus while, on the other hand, those of 

 the comparatively small C. echinata have had limbs and other remains of copepods obviously from 

 animals larger than the ostracod. Diatoms and other fine detritus could have been derived from 

 the copepods which had been eaten; frequently, however, as has been stated, such material may be 

 present without any copepod-remains. Furthermore, the appendages, particularly the proximal endite 

 of the maxillule, have, in addition to spines, an armature of slender setae and brush-setae, which 

 is reminiscent of a particulate feeder (cf. Cypridina antarctica according to Graham Cannon, 1933). 



Feeding on fine material 



Whether diatoms or detritus are deliberately collected by Conchoecia as food or are swallowed acci- 

 dentally is difficult to decide. There is no trace of any filter-feeding-structure in these animals, but there 

 are two ways in which such material could be collected. Muller's description of the observations upon 

 which he based his conclusions regarding the feeding of halocyprids provides evidence regarding one 

 of these. 



Muller described (1894, p. 109) how carmine particles, suspended in water in which Conchoecia 



