48 



ZOANTHARIA 



Colour in alcohol: tawny sand-coloured. 



External appearance. Tlie only colony of this species was attached to a frao^ment of a 

 Cidaris spine. The colony had a thin, disc-like coenench>ine from which two polyps emerged at a 

 long distance from each other. The polyps are elongated, narrow at the base and broader upwards. 

 The distal margin, which completely covered the tentacles, was truncate. The capitular furrows were 

 very indistinct. The incrustation of the polyps and the coenenchyme consisted of sand-grains, fora- 

 minifera and sponge-needles. The ccsophagus is short, the siphonoglyphe distinct. Hyposulcus? 



Anatomical structure. The ectoderm of the body-wall is high, sHghtly incrusted with the 

 above mentioned foreign bodies and detritus particles. In the distal part the nematoc5-sts are very 

 scarce, in the proximal part on the other hand nematocysts with coiled thread are common (length 

 22—29//, breadth 12 /^). The mesoglcea is thicker than the ectoderm, richly incrusted and contains 

 scattered, fairly numerous, often oval-shaped, granular cells of moderate size (PI. 7, fig. 3). In the 

 section figured, the foraminifera have been dissolved by means of nitric acid, so that only the cavities 

 in which they were lying can be seen. The ectoderm is thin. 



The sphincter is considerabh- shorter than in /. islaiidicits and has in the distal part some large 

 folds, which soon pass over into the ring-muscle layer of the body-wall. 



The tentacles, of which I made no macerated preparation, contained in the ectoderm numerous 

 spirocysts. Whether also thick-walled nematocyst capsules occur, I am unable to tell from the material 

 sectioned. 



The cvsophagus is as in /. is/andicus. 



In the examined specimen the number of mesenteries was 30, 9 macro- and 7 micro-mesenteries 

 on the one side, 8 macro- and 6 micro-mesenteries on the other. In the lowest part of the esophageal 

 region the micro-mesenteries are weak and only reach a little beyond the main lamella of the entoderm. 

 The macro-mesenteries are thin, the longitudinal and parieto-basilar muscles weak, but reach a long 

 way on the body-wall. The macro-mesenteries below the oesophagus seem to be longer than in 

 /. islandictts. 



The glandular tract of the filaments contains a few, large nematocysts with coiled thread (length 

 19 — 26(29)/^ generally 24, breadth 10 — 12 generally 10 — 11 /^) with rounded ends and fairly many, smaller, 

 similar capsules (length 12 — 14 /i, breadth 5 — 6 y). Further, there is a common occurrence of thick- 

 walled capsules, broader at the one end (length 14 — 17/^)- 



The sexual organs were not developed in the specimen sectioned. 



Remarks. See under /. islandicus. 



Isozoanthus danicus n. sp. 



PI. ., fig. 3-4. PI. 7, fig. 4. 



y.onntlnis couchii Go.s.se, Morten sen. Smaa biol. o. Faun. lagttagelser, Videnskab. Medd. 1897. p. 316. 

 Occurrence: Denmark, Limfjord. Mortensen; R. Horring Sept. 1902. Copenh. Miiseum R. M. 

 Dimensions. Height of the retracted polyps 0-25 — ■0-4 cm., breadth about 0'2 cm. 

 Colour in alcohol. The coenenchyme and the majority of the polyj)s dark or dirt\-colourcd. 



