THE HYDROID FAUNA OF THE WEST OF SCOTLAND 223 



Trophosome. Colony with compound stems and branches, the 

 latter being arranged in pinnate fashion. Hydroclades (ultimate 

 hydrotheca-bearing branchlets) often bearing on the lowest internode 

 a simple or branched secondary hydroclade more slender than 

 themselves. Each hydrotheca is accompanied by a single pair of 

 definitely placed lateral sarcothecos which are not fixed immovably 

 to it. Margin of hydrotheca smooth. 



Gonosome. Gonangia sac-shaped, springing from branches or 

 from hydrocladia, at the origin of the latter. 



The only British species is 



71. POLYPLUMARIA FLABELLATA, G. O. Sars. 



( = P. pumila, Allman). 



Trophosome. Colony attaining a height of 10 cms., composed 

 of fascicled stems, and fascicled branches which arise from the 

 stem in opposite pairs, and themselves bear opposite branches. All 

 of these lie in one plane and are furnished with alternate hydro- 

 clades arranged in no definite number on the internodes of an 

 anterior cladate tube. The hydroclades are only from i to 3 mm. 

 long, are set on a long process furnished with sarcothecas, and are 

 divided into internodes, on each of which, except sometimes the 

 basal, a hydrotheca is borne. The proximal hydrothecate internode 

 of a hydroclade gives rise to a simple or branched hydroclade, the 

 first internode of which bears only a series of nematophores. The 

 hydrothecse are cylindrical, widening slightly towards the mouth, 

 unattached to the internode, except at the rounded base. They are 

 accompanied by three definitely placed trumpet-shaped sarcothecas, 

 one proximal, placed medianly a little below the hydrotheca, 

 and two flanking the hydrotheca near its margin. In addition 

 there are generally present one, two, or three smaller sarcothecas, 

 lying in the median line of the internode above the hydrotheca. 



Gonosome. The gonangia, which were not observed on the 

 Scottish specimens, arise on the branches near the base of a primary 

 hydroclade. They are ovate, with obliquely truncated summit, a 

 short neck surrounded by a whorl of nematophores, and a short 

 peduncle. 



Localities. CLYDE SEA AREA. BARRIER PLATEAU - - fragment 

 of a colony from between Sanda Island and Ailsa Craig, 

 24 fms. 



FIRTH OF LORNE, 50-110 fms. A single complete colony, which, 

 although it is only 64 mm. high, less than half the size of 

 those collected by the " Travailleur " and "Talisman," shows 

 no lack of robustness in its finer structures, for measurements 

 of the trophosome agree in every detail with those of specimens 

 from the Bay of Biscay and the Azores recorded by Dr. A. 



