3°2 DISCOVERY REPORTS 



Conchoecia borealis antipoda, between i° S. and 65 S. in the Atlantic Ocean at depths of 470-1600 m. 

 The Discovery specimens used for study were taken at stations 138, 529, 661, 662 and 671 which 

 ranged from 43 08' S. to 57° 36' S. From the data provided by the samples taken with closing 

 nets the specimens would appear to have been captured at depths greater than 250 m. to below 

 1000 m. The species would appear to be a deep-water form. 



Miiller (1906) regarded Conchoecia borealis and C. antipoda as separate species, but Skogsberg (1920) 

 stated that the differences between them were too small to merit greater rank than that of a variety. 

 Both authors found the females to be larger than the males ; the Discovery specimens bear out this 

 difference in size. Skogsberg (p. 718) also found 'that the shoulder-vault had a sharp edge contrary 

 to what is stated by G. W. Miiller 1906', both males and females being alike in this character. In 

 the few males examined from the Discovery collections the shoulder-vault was sharp-edged but not 

 quite so far expanded as in the females. Skogsberg described the setation of the appendages in great 

 detail, but some repetition and further discussion has been found necessary in this report. 



The intensive study of C. borealis antipoda leads on to a comparison with other halocyprids, e.g. 

 Archiconchoecia, Euconchoecia and Halocypris and to a comparison of this group with the Cypridinidae. 



ACKNOWLEDGEMENTS 



I wish to thank the National Institute of Oceanography, and in particular Dr Mackintosh and 

 Dr Bargmann, for making their valuable collections available to me for study. My thanks are especially 

 due to Professor H. Graham Cannon for his continued encouragement and interest in my work. 



THE APPENDAGES, THEIR INTERRELATION AND FUNCTION 



Antennules (Figs. 1 and 2) 

 The antennules are uniramous and exhibit sexual dimorphism. Their shafts articulate antero-dorsally 

 with the body of the animal, close beneath the hinge of the carapace. They are normally directed 

 straight forward. 



In the male (Fig. 1 B) each is rigidly bound to the long slender shaft of the frontal organ by a single 

 pair of inner dorsal hooked seta. The three terminal setae are of great length. Of these latter, the 

 principal and one of the secondary setae bear an armature of spines and setules, which lock them 

 together for part of their length. Only the apices diverge. This armature differs in other species and 

 is a specific character of differential value. The setae are directed forward and slightly downward 

 through the anterior gape of the carapace. By flexure of the apical articles of the antennule, they can 

 be folded back and beneath the animal, between the bases of the appendages. Besides the principal 

 and secondary seta there are two so-called ' tube-setae ' near the apex of the antennule. These are 

 much shorter than the principal setae, stout, bluntly ending and very thin walled. 



In the female (Fig. 1 A) the shafts of the antennules are not locked to the frontal organ. The inner 

 dorsal setae extend forward to just beneath the rostrum. A single apical seta, corresponding to the 

 principal seta of the male antennule, is extended forward and downward, but its length is such that it 

 extends only slightly beyond the margin of the carapace (Fig. 2, a 1 s). The secondary setae of the 

 female are similar to the sensory tube-setae of the appendage of both sexes. In both sexes these 

 terminal tube-setae are carried hanging downward within the anterior gape of the carapace. 



It would seem that in the halocyprids the function of these appendages is largely sensory, though 

 there is no experimental evidence of this. The thin- walled tube-setae are of a type similar to other 

 ' chemo-sensory ' setae found in the Crustacea. They lie directly in the path of the water-current 

 flowing through the carapace, because they hang vertically in its anterior gape. The principal setae, 



