( 835 ) 



XXVII. — On an Entoproctan Polyzoon (Barentsia benedeni) new to the British 

 Fauna, with Remarks on Related Species. By James Ritchie, M.A., B.Sc, 

 Natural History Department, The Royal Scottish Museum. Communicated by 

 Dr R. H. Traquair, RR.S. (With One Plate.) 



(MS. received December 9, 1910. Read January 23, 1911. Issued separately April 18, 1911.) 



CONTENTS. 



PAGE 



(6) Arthropodaria benedeni and Barentsia 



gracilis ...... 843 



(c) Table of Dimensions .... 845 



(d) List of Synonyms .... 845 



PAGE 



I. Introduction 835 



II. Description of Specimens — 



Stolon 835 



Stalk 836 



Calyx 838 



Movements in Life 839 



III. Remarks on Related Species — 



(a) The identity of Pedicellina gracilis, Pedi- 



cellina belgica, Gonypodaria nodosa . 840 



IV. Systematic Relationship of Hull Specimens . 846 



V. Summary 847 



VI. Explanation of Plate 847 



I. Introduction. 



In February 1909 Mr John Thompson, Hull, forwarded to me for identification, 

 along with species of Hydroids, specimens of a " Pedicellina," which he was unable to 

 identify with any known British form. These specimens proved to be of particular 

 interest ; and although a first consignment was dead on arrival in Edinburgh, Mr 

 Thompson was successful in obtaining additional specimens, which, having travelled 

 safely, were kept under observation in a living state for a week, when they were 

 preserved for more detailed examination. Cocaine was found to be the most successful 

 narcotising agent. 



The specimens were all obtained from a single locality. They were found in the 

 St Andrew Dock Extension, Hull, growing on the surface of Membranipora which 

 clothed the under sides of horizontal timbers supporting the piles, and on the surfaces 

 of the timbers themselves. 



The most striking feature in these Entoproctan Polyzoon specimens was the jointing 

 of the stem ; and as jointed stems occur in but few species, from all of which our 

 specimens differ in some respects, a detailed examination was considered necessary. 



Before proceeding with the description of the specimens, I wish to express my 

 gratitude to Mr Thompson of Hull, to whose skill and enthusiasm as a collector is due 

 our knowledge of this interesting Polyzoon ; and to Drs S. F. Harmer and 

 J. H. Ashworth for assistance and advice. 



II. Description of Specimens. 



Stolon. 



The stolon is of the usual colonial Entoproctan type. Well developed, it reaches a 



considerable length, bearing sometimes as many as ten polyps, and being complicated 

 TRANS. ROY. SOC. EDIN., VOL. XLVII. PART IV. (NO. 27). 122 



