302 ERNEST ^YAKEEN. 



theca is practically sessile on a creeping stolon, and its height 

 is about -^^ inch. It is transversely annulated with about 

 twelve ridges, and the tetragonal mouth is stated to be 

 inopei'culate. The hydrotheca is rendered bilateral by the 

 slope of the neck towards one side. It was found at a depth 

 of thirty-eight fathoms. 



In Surtularella solitaria, found in shallow water at the 

 Bahamas, the hydrotheca is provided with a fairly long stalk 

 with one or two annulations near the middle. Hydrotheca 

 radially symmetrical, mouth quadrate, slightly everted, and 

 four equidistant teeth. Body of hydrotheca annulated with 

 about eleven transverse ridges. Operculum of four flaps. 



In both cases the anatomy of the hydranth is not touched 

 upon, but it is probable it is sertularian in nature as in S. 

 campanulata. It is curious that Calamphora parvula 

 is stated to be inoperculate ; S. solitaria and campaniilata 

 are both obviously operculate. 



It is interesting to note that, independently of the square 

 neck and mouth, the hydrotheca in both C. parvula and S. 

 campanulata exhibits a certain bilateral symmetry, thus 

 still further emphasising the sei'tularian nature of the hydroids. 

 In C. parvula the neck of the hydrotheca slopes towards 

 one side and the mouth is consequently not terminal and 

 radially symmetrical. In S. campanulata the peduncle of 

 the hydrotheca arises at an angle of 45° to the hydrorhiza, 

 and on the side facing the hydrorhiza the perisarc of the 

 hydrotheca is less than one-half the thickness of that on the 

 opposite side. The diaphragm, also, is excentrically perforated, 

 the aperture being on the side having the thin perisarc. 



Allman expressed some doubt as to how his C. parvula 

 should be classified, whether as a Sertularian or Campanu- 

 larian. The general habit of growth and apparent radial 

 symmetry of the three species would seem to place them 

 among the Campanulariida3 ; but the anatomy of the hydranth, 

 the operculated, dentate, quadrate mouth, and the real bilateral 

 symmetry, which exists under an exterior radial symmetry, 

 unmistakably point to sertularian affinities. 



