THE ECHIURIDAE, SIPUNCULIDAE AND 



PRIAPULIDAE COLLECTED BY THE 



SHIPS OF THE DISCOVERY COMMITTEE 



DURING THE YEARS 1926 to 1937 



By A, C. Stephen, D.Sc. 



The Royal Scottish Museum, Edinburgh 



INTRODUCTION 



THE extensive voyages of the Discovery Committee's ships in southern waters during 

 the years 1926-37 have resulted in a considerable and interesting collection of 

 Echiurids, Sipunculids and Priapulids being brought back. In all, sixteen species have 

 been identified in the collections. Of these one is new to science and one is now 

 recognized as being a larval form. The material has come mainly from the Antarctic 

 area, but some of the Sipunculids were secured in the Atlantic on the outward and 

 homeward runs. 



The collection possesses several points of interest. Although only one new species 

 is described, several are recorded from the Antarctic, Tristan da Cunha and Ascension 

 for the first time. In other cases the known range of distribution has been considerably 

 extended, thanks to the wide area over which the investigations were conducted. 



The Echiurids have supplied the most important records. Until the present col- 

 lections were made, the known representatives of this group in the Antarctic belonged 

 to three species— namely, Urechis chilensis from the coasts of Chile, Echhinis antarcticus 

 from South Georgia and Thalassenia verriicosum from Kerguelen. While the first two 

 species have again been taken in the original localities, there are now three other species 

 to be added. Two of these, Hamingia arctica and Thalassema faex, are well-known 

 species which have not so far been found in other than northern seas, and the third 

 is T. antarcticum, the only new species described. 



Most of the species of Sipunculids already recorded from the Antarctic have occurred 

 in the collections, some from new localities. The collections of Phascolosoma mor- 

 garitaceim have shown a considerably greater degree of variation than hitherto described, 

 and the variety trybomi, previously recorded only once from the Antarctic, has been 

 taken again. Physcosoma nigrescens is now recorded from the islands of Ascension and 

 Tristan da Cunha, as is also P. scolops from the first-named island. 



The Priapulids are represented by Priapiilus cmidattis var. tuberculato-spinosus only ; 

 this is rather surprising, since both P. bicaudatus and P. horridus have previously been 

 taken within the area of the investigations and might have been expected to appear m 

 the collections. 



