ZOANTHARIA 43 



Isozoanthus arborescens (Dan) Carlgr. 



PL I figs. 1 2, PI. 2 fig. 27, PL 3. fig. 5, PL 6, fig. 2. 



Epizoanthus arborescens n. sp. Danielssen Norw. North Atl. Ex. Actinida. 1890. Tab. 6 fig. 6 Tab. 24 



figs. 14. 

 Isozoanthus arborescens (Dan) Carlgren in Nordgaard 1905 Investig. in Norwegian fjords p. 159. 



Occurrence: 6o37' N., 2752'W., 799 Dan. fms. Bott. temp. 4-5. Ingolf Ex. i spec. 



65 28' N., 27 39' W. 450 Dan. fms. Bott temp. 5-5. Ingolf Ex. St. 97 5 spec. 



67 52' N., i358'E. 247m. clay Bott. temp. 4-9. Norw. North Atl. Ex. 23/6 1877. St 149. 

 Bergen M. R. M. 



S. E. of Mortsund 200 m. Bott. temp. 6-6. 22/2 1899 Nordgaard. i colony. 



12 miles E. by S. of Reine 150 m. 3/3 1899 Nordgaard. 2 spec. 



68 15' 5" N., i549'E. Tranodybet 6076401^ Bott. temp. 6-3. 16/3 1899 Nordgaard. 



Dimensions in the expanded state, probably measured on living specimens: "up to 3-5 cm. 

 in length with a basal part only 0-5 o - 6 cm., the uppermost extremity i '2 cm. in breadth." Danielssen. 

 The largest specimen from the Ingolf Expedition had in preserved state a length of 2'8 cm., a 

 breadth at the base of 0-2 cm. and at the apex of 0-35 cm. 



Colour according to Danielssen. "The incrusted portion of the body is grey with a play 

 of a slightly greenish colour. The oral disc is almost white with a reddish tinge. The tentacles pale 

 rosy-red." 



External appearance. Danielssen has given a good description thereof. The polyps are 

 solitary and connected with each other by a very small ccenenchyme attached to stones (or Serpula- 

 tubes or similar objects, see Danielssen fig. 6, Tab. 6, fig. i, Tab. 24). The colonies are often attached 

 by means of a thin membranous part, from which an inconsiderable tube-shaped ccenenchyme extends 

 sending out numbers of polyps which make the colony look like a plant branching off at the base. 

 Though not a little incrusied the polyps are rather slender and very elongated with a narrow, long 

 basal part, which gradually becomes broader towards the distal part. In the contracted polyps the 

 broadest part lies a little way from the distal end. The polyps from Mortsund (fig. i PI. i) were 

 strongly contracted and consequently very firm, and the basal part of the polyps did not project so 

 much as in the other, more developed polyps from other localities. Danielssen states that they have 

 16 capitular furrows. On the preserved specimens these are however very indistinct and only in the 

 Mortsund specimens have I been able to trace them. The body-wall is incrusted with sand-grains, 

 though not in very great quantities, so that "when the animal is extended and in full vigour, they 

 permit the white-red integument to shine through it." (Danielssen). 



The number of tentacles agrees in all probability with the number of mesenteries, in which 

 case it is 3236. The innermost row of tentacles are according to Danielssen very long. The same 

 author also states that the oral disc is "rather flat and finely folded, the oral aperture is almost circular." 



The oesophagus is short with well-marked siphonoglyphe and distinct hyposulcus. 



Anatomical description. Danielssen has described the anatomy of this species but as 

 usual very unsatisfactorily, especially with regard to the musculature, which according to his work 



