LAFOEA GRACILLIMA. 13 



hydrotheca in the specimens in which, even when stained, I can find no 

 trace of teeth, only an operculum, which adds to the difficulty of deciding 



the generic relations of this peculiar form with both teeth and operculum. 

 As the gonophores are unknown there is far too little basis for creating even 

 a provisional genus for these peculiar hydrothecae. 



It is interesting to find a species which combines the general shape of 

 the hydrothecae of the Campanulinidae with the campanulate forms of the 

 Campanularidae ; and the operculum combined with teeth is a new combina- 

 tion. Teeth may have sometimes developed into opercula, but this would 

 seem to be a case where the operculum originates at the same place of 

 growth activity as the teeth. In those hydrothecae with the triple rows of 

 teeth the two additions to the length of the hydrothecae may have come 

 about through the growing together of the proximal parts of the segments 

 of the opercula, or, as would seem more probable, by a new cylindrical 

 growth having a toothed rim, after either of which processes there would 

 have been the growth of a new operculum. The latter method would be, 

 with the exception of the formation of the teeth, like the secondary growths 

 seen in Calycella syringa, as shown by Nutting J and by Levinsen. Figure 

 17 of Levinsen 2 forms an especially interesting comparison, as in that the 

 segments of the original operculum are retained. 



Lafoea gracillima Alder. 



One small specimen of this delicate species was brought up by the 

 "Tansies" from Station 4642, five miles southeast from Hood Island, 

 Galapagos Archipelago ; depth, 300 fms. ; bottom, broken shells and 

 Globiyerinae. 



This species, so far as I am aware, has been found hitherto only in 

 northern waters : North Atlantic, Bonnevie 3 ; Alaska, Clarke 4 ; Yellow 

 Sea, Marktanner-Turneretscher 5 ; Coast of Maine, Verrill. 6 Its occur- 

 ence at Station 4642 brings it about two degrees south of the equator. 



1 Bulletin U. S. Fish Comm., 1899, p. 354. 



2 Om Fornyelsen af Ernaeringsindividerne hos Hydroiderne. Saertryk af Vidensk. Meddel. fra 

 den naturhist. Forening i Kjobenhavn. 1892. 



3 The Norwegian North Atlantic Expedition, Zoology, Hydroida, Christiania, 1S9!>. p. 65. 



4 Scientific Results Exploration of Alaska, W. H. Dall, Smithsonian Institution, Washington, 

 1876, p. 1-2. 



5 Annalen des K. K. Naturhistorischen 1 1< if museums, 5, s. 217. 



6 Amer. Journ. Sci., April, 1871, 7, p. 413. 



