ASCIDIACEA 



By R. H. Millar 

 Marine Station, Millport 



(Plates I-VI, text-figs. 1-72) 



INTRODUCTION 



The ascidians which this report describes were collected during the years 1925-37 by R.R.S. 

 'Discovery', R.R.S. 'Discovery II', R.R.S. 'William Scoresby', and the staff of the Marine 

 Biological Station at South Georgia. A large part of the material is from the Falkland Islands and 

 Patagonian shelf in the Subantarctic, and much was also collected from the vicinity of Graham Land, 

 South Georgia and the South Shetland, South Orkney, and South Sandwich Islands in the Weddell 

 Sea sector of the Antarctic. Of the many other localities represented, one of the most interesting is 

 the Three Kings district at the northern end of New Zealand. 



There are altogether about 2500 specimens, representing seventy-eight identifiable species. Of 

 these, thirteen are described as new and there are three new forms of known species. The type 

 specimens are deposited in the British Museum (Nat. Hist.). 



LIST OF NEW GENERA, SPECIES AND FORMS 



Aplidium falklandicum sp.n. Podoclavella kottae sp.n. 



A. stanleyi sp.n. Sycozoa anomala sp.n. 



A. quadrisulcatum sp.n. Cnemidocarpa tricostata sp.n. 



A. seeligeri sp.n. Styela schmitti f. simplex n. 



Aplidiopsis discoveryi sp.n. Molgula setigera f. georgiana n. 

 Protopolyclinum gen.n. ,, >> *■ ^nanoni n. 



P. pedunculatum sp.n. Eugyra brezvinae sp.n. 



Ritterella vestita sp.n. E. drnbdckae sp.n. 

 Didemnum trivolutum sp.n. 



The task of working through the material was greatly eased by the fact that Dr A. Arnback-Christie- 

 Linde had completed the process of sorting the collection before her death. She also made prelimi- 

 nary identifications of a number of the specimens and left notes on some of them. Her notes, which 

 were made available to me, have been very valuable. Nevertheless, I have had to re-examine all the 

 material, and this report represents my own views, which differ in many points from those which 

 Dr Arnback-Christie-Linde would have expressed had she lived to write the account of the Ascidiacea 



from the ' Discovery ' collections. 



CLASSIFICATION 



I have adopted the classification used by Huus (1937-40) in Kiikenthal and Krumbach's Handbuch 

 der Zoologie, with the following modifications : 



In the order Enterogona, suborder Phlebobranchiata I have recognized the family Diazonidae 

 Garstang, 1891, as distinct from the family Cionidae Lahille, 1887, using these groups as defined by 

 Berrill (1950). Ciona occupies a somewhat isolated and probably primitive position, indicated 

 especially by the failure of the two epicardia to fuse and by the position of the gut (Berrill, 1936), 

 and therefore merits a family to distinguish it from the diazonids (Diazona, Tylobranchion, Rhopalea). 



