HYDROIDA II 



167 



Laonicdea geniciilata is a cosmopolite, belonging to tlie npper part of the littoral region; in 

 northern seas it is chiefly restricted to the Lafiiiiiaria, bnt may also occnr on deeper-growing Zostcra 

 and on shallow red algK in large qnantities. Albeit properly cosmopolitan, the species is nevertheless 

 very rare in strictly arctic waters, bnt may occur here right into the White Sea. It is most frequent 

 in the boreal areas. Along the coasts of Norwaw round the British Isles, the Faroe Islands and Ice- 

 land it is present in great nnml^ers (fig. L,XXXV). It is also mentioned from Greenland, but no de- 

 finite locality has yet been recorded. 



200 m. 600m. looom. 



Fig. LXXXV. The distribution of I.aomedca gcniciiUita in the Northern .\tlantic. 

 In the hatched regions the species is abundant. 



Laomedea longissima (Pallas) Alder. 



1766 Sertularia longissima^ Pallas, Elenchus zoophytorum, p. 119. 



1858 Laomedea — , Alder, A Catalogue of the Zoophytes of Northumberland, p. 121. 



1868 Obelia — . Hincks, A History of the British Hydroid Zoophytes, p. 154, pi. 27. 



1868 — fiahfllata^ Hinck.s, I.e. p. 157, pi. 29. 



Large graceful colonies witli monosiphonic, brown stem, generally fle.xuous. I'roni this pro- 

 ceed secondarily ramified branches, which again give off a hydrotheca stalk from the apophxse at 

 each bend. There is no thickening of the periderm under the apophyses. The hydrothecK are about 

 twice as long as broad, slender, inversely conical, with more strongly ctirved basal part. Tlie hydro- 

 theca margin is more or less curved, at times with distinct teeth, at others quite .smooth. The basal 

 chamber is fairlv large, and bounded at the top by a finely built Init distinct diaphragm. 



