THE APPENDAGES OF THE HALOCYPRIDIDAE 



By E. J. lies 



(Department of Zoology, The University of Manchester) 

 (Text-figures 1-14) 



INTRODUCTION 



A prolonged systematic study of ostracods has impressed me with the remarkably constant 

 pattern of the structure, even to the fine details of setation, of the appendages of the Halo- 

 cyprididae. In earlier literature (Muller, Claus, Sars, Vavra), brief descriptions of the anatomy of 

 these animals are to be found, but they usually refer only to isolated limbs or to the carapace. More 

 recently Skogsberg (1920, 1946) has given minute details of the structure and setation of appendages in 

 a number of species, but nowhere is there a description of the anatomical and spatial relationship of 

 the various limbs to each other. This is essential to the proper understanding of the functional 

 morphology, the way in which the limbs are used, which, in its turn, is essential as a background to 

 further advances in the study of the taxonomy and thus the evolution of the group. The following 

 paper is an attempt to supply this deficiency. 



The family Halocyprididae is included in the Myodocopa, which is characterized as follows : shell 

 generally with an antennal notch ; seven pairs of appendages ; frontal organ usually present ; antenna 

 biramous with well-developed propod, exopod multiarticulate and bearing natatory setae, endopod 

 normally small and often prehensile in the male; mandibular palp pediform; caudal furca with 

 lamellar rami bearing marginal spines. All the members of the Halocyprididae are planktonic and 

 have appendages adapted to this mode of life. 



Although numerous species have been studied during the course of my work, one was selected for 

 intensive study, namely Conchoecia borealis G. O. Sars var. antipoda G. W. Muller, not because it is 

 more typical of the group than any other species, but because material fixed in alcoholic bouin was 

 available in the Discovery collections. This had been very kindly handed to me by Professor H. 

 Graham Cannon. The material was suitable for cutting wax sections which could be used to check 

 certain features of anatomy. Formalin-fixed material also available from the Discovery collections was 

 unsuitable for embedding in wax. It was used, however, for the preparation of thick celloidin sections 

 for study by methods similar to those described by Professor H. Graham Cannon (1933). The greater 

 part of my work on the group, however, has been carried out by the use of fine or microdissection 

 methods. After removing the carapace, antennules and frontal organ, the remaining appendages of 

 the left side of the animal were separated by cutting the arthrodial membranes by which they articulate 

 with the body. By this means, not only could an independent study of the isolated appendages be 

 carried out, but the body of the same animal could be mounted left side uppermost. With sufficient 

 care in dissection, the relationship of the inner faces of the undisturbed appendages of the right side 

 could then be studied. In preserved material the appendages occupy a range of positions which must 

 represent those which they could take up during life. Study of a number of such specimens and the 

 articulation and musculature of their appendages has been of value in interpreting the observations 

 of live animals made by Muller (1894). 



Muller (1906), whose figures were quoted by Skogsberg (1920), gave a very wide distribution for 



