c 2 ZOANTHARIA 



Anatomical description. The ectoderm of the body-wall is continuous, fairly high and 

 contains fairly many, uniformly broad nematocysts with greatly twisted thread — length (38)41 — 48/z, 

 breadth 14 — 17 p- The ectoderm and outer part of the mesoglcea are strongly incrusted, almost ex- 

 clusively with black sand-grains interspersed with a few sponge-needles. The mesoglcea is thick, the 

 inner half and probably also the outer one (owing to the strong incrustation it has been rather difficult 

 to study the structure of the mesoglcea) contains cells and numerous cell-islets (PI. 6, fig. 3), the majority 

 of which are small but others reach quite a considerable size though not so large as in I. magninsulosus. 

 More seldom the cell-islets fuse together to form elongated lacunae but not so great as in /. magnin- 

 sulosus. An encircling sinus however is not found. The entoderm is thin, with black pigmentation. 



The sphincter is entodermal, long and in the upper end has some fairly deep, often large folds. 



The ectoderm of the tentacles is high and contains numerous spirocysts, besides many thick- 

 walled nematocysts (length 19 — 24 /z) and a few large capsules with greatly twisted thread of the same 

 kind as in the body-wall, but somewhat small (34 /i long). 



The ectoderm of the oesophagus is fairly high and contains numerous thick-walled capsules 

 (length 22 — 24 /i), and the same kind of large nematocysts as found in the body-wall though somewhat 

 smaller (38 — 41 ji long). The mesogloea is thin and considerably weaker than in the siphonoglyphe, 

 whose ectoderm as usual is lower than that of the oesophagus. 



In the two specimens examined the number of mesenteries was 38 and 40. The second polyp 

 was typical, the first had 1 couple of mesenteries more on the one side than on the other. The micro- 

 mesenteries are moderately developed even below the oesophagus and several times broader than the 

 entoderm of the body-wall. The mesogloea of the mesenteries is thin, the longitudinal musculature 

 weak and partly folded, the parieto-basilar muscles weak. The extension of the longitudinal and 

 parieto-basilar muscles on the body-wall is distinct though not considerable. Below the oesophagus 

 the mesenteries are narrow, so that the gastrovascular cavity is large. 



The filaments have the usual structure. In the glandular tract there is a rich occurrence of 

 large capsules of the same kind as in the body-wall (length 41 — 48^, breadth 14 — 17 p) and a sparse 

 occurrence of similar smaller capsules (length 17 — 19 «, breadth 7^); further, it contains fairly many 

 thick-walled capsules with distinct basal part to the spiral thread and somewhat broader at the one 

 end (length 22—24//, largest breadth 6pi). 



The sexual organs were not developed in the specimens examined. 



Isozoanthus ingolfi n. sp. 



PI. 2, fig. 25. PI. 6, fig. 6. 



Occurrence. 64°54'N., 55°io'W. 393 fms. Bott. temp. 3-8°. Ingolf Ex. St. 27 several spec- 

 imens (type). 



Finmarken Ogsfjord Loven, 1 colony with 2 polyps. 



Dimensions. Largest polyp (from Davis Straits) 1 cm. long and 0-550111. broad. 



Colour in alcohol: light sand-coloured, the specimen from Finmarken containing small, scattered 

 black sand-grains. 



