HYDROIDA II 



69 



lower parts of the same; it has been met with once or twice quite deep down in the abyssal region, 

 as for instance 011 the "Thor" expedition, when it was taken near the Faroe Islands at 872 metres, 

 probably the greatest depth from which the species has hitherto been recorded. Nemertesia ramosa 

 belongs to the warmer parts of the Atlantic, and penetrates thence (fig. XXXIII) in great numbers 

 into the southern part of the boreal region. The species has not hitherto been found in Greenland 

 waters, but is recorded fiom one or two places on the south coast of Iceland. Round the Faroe Is- 

 lands, it is seen to be of very frequent occurrence, and is said by Hincks (1868 p. 283) to be more 

 numerous even than Nemertesia antennina on the coasts of Scotland. The species has not yet been 

 located with certainty on the Norwegian coasts, but its occurrence in the Skagerak (Broch 1905 p. 

 24) and Bohuslan (Jaderholm 1909 p. 105) suggests that it will probably be found to occur there. 1 



Polynemertesia nov. gen. 



Upright colonies with distinct, branched main stem, exhibiting segmentation in its monosipho- 

 nic parts; the stem is furnished with alternating strong apophyses which bear finely built hydrocladia. 

 The hydrocladia are secondarily branched. The apophyses both those of the primary and those of 

 the secondary hydrocladia - - are furnished on their upper side, near the point of origin, with a 

 short sessile sarcotheca, "mamelon"; all the remaining sarcothecse are mobile. The primary and se- 

 condary hydrocladia are segmented, and bear several hydrothecae, which are as a rule fused through- 

 out their entire length with the branch. 



It is with considerable hesitation that I have established this new genus for Plumularia gra- 

 cillima G. O. Sars. Previous investigators have overlooked the presence of a "mamelon" on the apo- 

 physes, in virtue of which the species must be separated from the Plumularia. With its secondary 

 ramification of the hydrocladia, however, the species stands in the same relation to Nemertesia as 

 Polyplumaria to Plumularia. A separation of the two latter genera therefore logically demands a 

 like separation between the parallel groups of Nemertesia and Polynemertesia. The fact that the prim- 

 ary apophyses in the only known species are biserially arranged on the hydrocaulus must be regarded 

 as of minor importance. 



It might be thought more reasonable here to revive an older name for the genus in question ; 

 it should then be Diplopteron or Schizotricha. The former, however, has already been withdrawn by 

 Allmann himself (1883 p. 30) as synonymous with Polyplumaria; Nutting's attempt to revive it (1900 p. 

 81) can only be explained as due to his having taken as basis for the generic division a character 

 which should otherwise be used only with caution even in distinction between species, as in all pro- 

 bability, it would seem that the type species for Polyplumaria and Diplopteron are very nearly identi- 

 cal. And with regard to Schizotricha it should be borne in mind that both the two species originally 

 placed by Allman (1883 p. 28) in this genus must be referred to Polyplumaria. It would thus be 

 incorrect to take as the type a species which has not from the first been ascribed to this genus; Plu- 

 mularia gracillima G. O. Sars is first placed under this head by Nutting (1900 p. 80). Of the remain- 

 ing species which have been referred to this genus, Schizotricha bifurca Hartlaub and Schizotricha 



After the close of the manuscript a find of the species in the Trondhjetn fjord has proved the correctnes of this 

 supposition. 



