CERIANTHAKIA. 

 30 



to be a rather great difference between A. albida and A. sarsi, in that the former's protomesenteries 2 

 are provided with extremely well developed cnido-glandiilar tracts, which I have not been able to 

 discover in the latter. However, as the specimen of A. sarsi is not in every respect well preserved, 

 and is so scanty, I mnst leave the connection of Arachnanthus sarsi and Arachnadis albida an open 

 question. In the diagnosis above I have bracketed the arrangement and appearance of the tentacles, 

 as these characters are only transferred from the free swimming larval stage of A. albida. 



Lastly, I mnst mention that in a previous work (Nordisches Plankton 1906) I wrongly suggested 

 that the adult species answering to Arachnadis albida was to be looked for in a gigantic Cerianthid 

 (in fact the species here described Padiyccrianthus mtdfiplicahis). This hypothesis has not been con- 

 firmed by the anatomical investigations, although the appearance, great length and probably also the 

 arrangement of the tentacles are much the same in P. iiiultiplicatus and A. albida. 



Family Botrucnidiferidae Diagnosis see Section III. 

 Genus Botrucnidifer nov. gen. Diagnosis see Section III. 



B. norvegicus n. sp. PI. 4, fig. 6—8, PI. 5, figs. 9—10. 



Diagnosis. A small species with rather few tentacles. The marginal tentacles 34 at most, the 

 labial tentacles 17 at most: the labial tentacles are consequently considerably fewer than the marginal 

 ones. In relation to the size of the animal the tentacles are of moderate length. Arrangement of 



tentacles: Marginal tentacles i (dt) 4. 3, i j 3, 2, 3, i 3, 2, 3, t | 3, 2, 3, i Labial tentacles o (dt) 0,1,1 



I, I, I, I , The labial tentacles not developed above directive chamber and the contiguous chamber 



on either side of it. The stomatodaeuni of medium length. The siphonoglyph narrow but deep, with 

 onl>- the directive mesenteries attached to it, with no hyposulcus, and very slight hemisulci. The 

 directive mesenteries very short, with no differentiation of filament. Protomesenteries 2 fertile, reaching 

 right down to the aboral end of the animal, with a region of the ciliated tracts, a region of the cnido- 

 glandnlar tract, a long craspedion region, and a small botrucnid region. Protomesenteries 3 sterile, 

 rather shorter than the former and resembling them, but with shorter craspedion region and larger 

 botrucnid region. The metamesenteries of the ist and 2nd cycles are like protomesenteries 2, but 

 shorter, the difference in length between the mesenteries of cycles 1—4 in the same quartette is not 

 so great as in other Ceriantharia. The regions of the ciliated tracts of medium length in all mesen- 

 teries and without craspedonemes. The cnido-glandular tracts in protomesenteries 2 and 3 and the 

 metamesenteries are not very far from the stomatodaeuni. In metamesenteries 2 they are about as 

 far from the lower border of the stomatodaeuni as the length of the stomatodaeum itself. Well devel- 

 oped craspedion region especially in protomesenteries 2 and the metamesenteries of the ist and 2nd 

 cycles. The botrncnids in the most aboral portion of the mesenteries, most developed in protomesen- 

 teries 3 and the metamesenteries of the 3rd and 4th cycles. 



