CBRIANTHARIA. 



Family Acontiferidae Diagnosis see Section III. 



Genus Arachnanthus nov. gen. Diagnosis see Section III. 



A. Sarsi n. sp. 



Diagnosis: (Marginal tentacles long, tapering very gradually towards the point? Labial ten- 

 tacles well developed? Directive chamber and the contiguous chamber on either side of this without 

 labial tentacles?) Stomatodaeum of medium length with very long hyposulcus that reaches past the 

 middle of the animal and exceeds the Stomatodaeum in length. The directive mesenteries comparatively 

 long but do not extend farther than the middle of the hyposulcus. The protomesenteries of the and 

 cycle of the length of the hyposulcus, probably sterile, without cnido-glandular tract. Protomesenteries 

 3 about the length of the directive mesenteries with very short ciliated tract-region and very long 

 cnido-glandular tract region. The metamesenteries of the and cycle almost as well developed as those 

 of the ist (M). The oldest mesenteries of the ist and 2nd cycle long, reaching not quite down to 

 the aboral end of the animal, fertile, with long ciliated tract region. The ist metamesentery on each 

 side with an "acontium". The metamesenteries of the 3rd (B) and 4th (b) cycle short, about the length 

 of protomesenteries 3, sterile, with very short ciliated tract region and very prolonged cnido-glandular 

 tract, b slightly shorter than B. The musculature of the mesenteries comparatively well developed. 



Occiirrcnce. Trondhjem fjord. Roberg Indalbay 140 m. Silted sand with shells and small 

 stones 18.6.1901. I. Arvidsson, R. M., i ex. 



Dimensions in extended state: Length 47 cm. , greatest breadth o - 8 cm.; in preserved state: 

 length 3-2 cm., breadth 07 cm. N. B. the uppermost part of all was torn away. 



Colour according to Arvidsson. "Mouth (Stomatodaeum or oral disc?) dark brownish-black. 

 Column yellowish-white with yellowish-brown longitudinal stripes, which are absent in the front. The 

 most distal portion is fairly transparent, so that the Stomatodaeum and the white mesenteries gleam 

 through". 



Exterior aspect. Body of the form characteristic of Ceriantharia. Of tentacles no trace is found, 

 but this does not signify that we have here a species devoid of tentacles; in all probability the ten- 

 tacles have been torn off together with the topmost part of the body, whereupon the Stomatodaeum 

 has coalesced with the column. For the Stomatodaeum quite distinctly passes straight into the column 

 and no oral disc is discoverable. Thus the animal is plainly in a state of regeneration as far as the 

 front part is concerned. The Stomatodaeum is well developed and of the structure characteristic of 

 the Acontiferidae. The siphonoglyph is very broad. The hyposulcus is very long, exceeding the 

 length of the Stomatodaeum, and also very broad. The upper half is attached to the directive mesen- 

 teries in the form of a broad groove, whilst the aboral half is free. The lower free border is rounded, 

 so that no differentiated hemisulci are found (See the diagram. Textfig. 5). 



Anatomical structure. As I have only had one specimen for study, I did not like to dissect it 

 fully, especially as the mesenteries are not very well preserved. The description of the anatomical 

 structure therefore remains incomplete. 



The column is like the other Ceriantharia in structure. The ectoderm is very thick and 



4* 



