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Note on Two Unrecorded Plumularian Hydroids 

 from the Plymouth Area. 



By 

 James RitcMe, M.A., D.Sc, 



Royal Scottish Museum, Edinhuryh. 



Confusion has reigned in the works of British authors as to the relation- 

 ship between Plumularia catharina, Johns., and a more simple form, 

 with unbranched stem, found, like the former, on many parts of the 

 coast. Johnston and Hincks, and the majority of their successors, have 

 recorded the simple form, where it was thought worthy of mention, as 

 a " stemless variety " of the former ; but examination of the type 

 specimens of P. catharina in the British Museum has proved that a 

 fundamental distinction exists between the two forms.* P. catharina 

 is a branched species and bears on each side of a hydrotheca a fair of 

 lateral sarcothecce ; the other is a branchless, bristle-like form, bears on 

 each side of a hydrotheca a single lateral sarcotheca, and has been long 

 known as Antenella (or Plumularia) secundaria (Gmelin). 



One of the most common of Plumularias in the Plymouth area, in a 

 wide sense, is P. catharina, and in a recent paperf IVlr. Crawshay records 

 the " creeping variety " from many stations in the Outer Western Area 

 of the English Channel, with the remarks that it occurred over the whole 

 area, and that it was perhaps the most frequent of the two varieties,, 

 and was certainly the most flourishing in point of growth. 



I have had the opportunity, thanks to Mr. Crawshay, of examining 

 a few samples of the simple form, and find that it embraces two distinct 

 species, which are different from P. catharina, and have not been recorded 

 from the area. The most common of these is Antenella secundaria 

 (Gmelin), distinguished by a simple stem, and by details of hydrotheca 

 structure exceedingly like those of the erroneous figure of P. catharina 

 given by Hincks in " British Hydroid Zoophytes," Plate LVI, Fig. 2a. 

 It was found at Duke Rock in August, 1895, and was dredged in the 



* See Ritchie, " Note on the Type Specimens of Plumularia catharina," etc., Proc. 

 Roy. Physical Soc, Edinburgh, Vol. XIX, 1913, p. 1. 



t Crawshay, Jbi^ni, Marine Biol. Association, Vol. IX, ]912, pp. 279 and 330. 



