S6 HYDROIDA II 



Material: 



"Ingolf" St. 25 6 3 °3o' N, 5 4°25' W., depth 582 fathoms 3,3° 



- 29 6 5 ° 3 4' N, 54° 3 i' W, - 68 0,2° 



- 34 6 5 °i 7 ' N., 5 4°i 7 ' W., - 55 



- 93 6 4 °24' N., 35^14' W., - 767 1,46° 



- 97 6 5 °28' N, 27*39' W, 450 5,5° 



- 127 66°33' N., 2o°o 5 ' VV., 44 5,6° 



Greenland: Davis Strait, depth 80 fathoms (without further details) [type specimen of Clado- 



carpus crenulatus] 

 ^5°39' N., 28°25' W., depth 553 fathoms [type specimen of Cladocarpus crenulatus\, 



Cladocarpus formosus is described in detail by Ritchie (1909) from some colonies taken at 

 about the same place as Allman's type specimens. Among the features which he here notes is 

 the fact that the opening margin of the sareothecae is "serrate". Most of the present colonies fully 

 agree with Ritchie's careful description. We have, however, from the "Ingolf" St. 25, in addition 

 to many typical colonies, also some few of slightly different structure (fig. XL-V). The hydrotheece 

 are here somewhat broader than the normal, the septum is set a little deeper down, and goes consider- 

 ably farther in towards the adcladial side than in ordinary colonies of the species, while on the other 

 hand the internodial jibs are less pronounced, and fewer in number. Furthermore, all the sareothecae 

 here have smooth opening margin. The points of difference, as compared with the typical form of 

 Cladocarp//s /<>r///osus, are thus sufficiently marked; they are however, too slight to warrant our mark- 

 ing off a distinct species, since no other differences can be discerned. The colonies should thus merely 

 be regarded as representatives of a special variety within the species. 



Ritchie (1909 p. 314) points out that Levinsen's Cladocarpus crenulatus (1893 p. 68) must 

 be regarded as a synonym of Cladocarpus formosus; and after having examined Levinsen's type 

 specimens, I must entirely concur in this view. Bonnevie (1899 p. 95) mentions Aglaophenia formosa 

 from a station near Spitzbergeu; her description however, differs not a little from Allman's, and 

 from those of later writers; in the first place, no mention is made of the intrathecal septum, in addi- 

 tion to which, the description of the hydrotheca as "almost cylindrical, regularly dentated round the 

 margin" is hardly in accordance with what we otherwise know of the species; the published drawings 

 (1898 Tat 2, fig. 3) also differ somewhat, so that the identity of the colony seems doubtful. An investi- 

 gation of the type specimen, however, shows that the intrathecal septum is present, and that the spe- 

 . cimen only differs from the colonies here in question in the somewhat more distinct and regular den- 

 tition of the hydrotheca margin. In addition, one of the phylactogonia is piunately branched, as in 

 Cladocarpus paradiseus Allman, while the others are dichotomically branched. 



Cladocarpus formosus is plainly one of the most common forms in the warmer tracts belonging 

 to the upper part of the abyssal region in the North Atlantic (fig. XLVI) and penetrates thence up 

 into the lower part of the littoral region. It is originally known from the southernmost part of the 

 cold area, where the latter runs into the Faroe Channel, but should here be regarded as a visitor, 

 brought iu by larval transport with the Atlantic current. The species is previously known from 



