HYDROIDA II 

 34 



It is evidently this species which is partly mentioned nnder the term Lafoea pygviaa; according 

 to Hincks (1868 p. 205) some of Alder's original drawings show a conical lid in this species, which 

 at once shows that Alder's specimens, or at any rate some of them, mnst have been Calycella syringa. 

 That Lafoea pygmcea is here only partly noted as synonymous with this species, is, as indicated under 

 Lafoea gracillima, owing to the fact that several writers at any rate have recorded creeping colonies 

 of the latter species under the same name. 



Calycella syringa appears to be a wholly cosmopolitan species, which has been met with in all 

 seas. Its bathymetrical area is very extensive, ranging from about 6 metres down to nearly 1500; it 

 should nevertheless be observed that its occurrence in the abyssal region is exceptional, its chief area 

 of distribution being restricted to the middle and upper parts of the littoral waters. Withiu the area 

 investigated (fig. X) we find that it is apparently lacking 'along the greater part of the east coast 

 of Greenland, where it is first met with far to the north, about 76° N. Its occurrence under high arctic 

 conditions is altogether scattered, save where an intermixture of warmer water is discernible. 



Gen. Tetrapoma Levinsen. 



Stolonial colonies with tubular or narrowly bell-shaped hydrotheca; without diaphragm. Closing 

 apparatus formed by the original roof of the hydrotheca, and separated b\- a marked limitation from 

 llie thicker hydrotheca wall; it con.sists of (four) separate triangular plates, each attached in a sinus, 

 between as many hydrotheca teeth. The polyps have a uniformly developed gastral endoderm, and 

 lack outer ectoderm lamellse. 



In a previous work (1909 p. 165) I united this genus with Lovenella. Kramp (1911 p. 383) 

 separates tliem again as two genera, chiefly, it would seem, on account of the number of plates in 

 the lid. This feature can hardly be called important as a generic character; there is, however, another 

 distinguishing feature of greater significance, which renders it necessary to separate the two genera. 

 Hincks (1868 p. 178) especially mentions in Lovenella clausa (Loven) the presence of a diaphragm, a 

 formation which does not appear to be found in Tetrapoma qiiadrideiitatum^ and which warrants generic 

 distinction. Secondarily, this separation is supported by the fact that Tetrapovia has stolonial colonies, 

 while those of Lovenella are sym])odial.' 



lycvinsen (1913 p. 283) observes in a footnote, regarding Tetrapoiia, "This genus must, no 

 doubt, be united with Thyroscyphus'\ In this I am for several reasons unable to concur. In the first 

 place, Thyroscyphiis has a distinct diajjhragm, and hydrothecae of bilateral structure; in the second, 

 the structure of the pol)-]) also is entirely different. Thyroscypfi/is, with its ectoderm lamella: and inci- 

 pient Ijlind sack formation, as also the differentiated gastral endoderm, exhibits closer relationship with 

 Sertulariidcc, and should probably far rather be considered as a primitive genus of this family. 



Tetrapoma quadridentatum (Hincks) Levinsen. 

 1874 Callycclla guadridentata, Hincks, On deep-water Hydroida from Iceland, p. 149, pi. 8, figs. 17 — 20. 

 1893 Tetrapoma (j7iadridentatnvi, Levinsen, Meduser, Ctenophorer og Hvdroider, p. 180. 



' Coiiip. also Lovenella corriigata Thorncly ilirocli 1914 p. 32). 



