ACTINIARIA 



231 



Dimensions in presented state: L,ength of the largest specimen 6,8 cm, breadth of the base about 

 3,8 cm, the outer tentacles about 0,3 cm long. 



Occurrence: West Greenland. Ritenbenk 15 — 20 fms. (Oberg). Julianehaab 5 — 10 fms. (Am- 



mondsen 1865). Davis Strait 6o°4o' N. 55°54' W. 150 fms. 

 (Tjalfe-Exp. 1909). 69°i7' N. 52°5o' W. 225 fms. (Tjalfe-Exp. 1908 

 St. 117— 118). 

 Greenland without distinct locality. 



Exterior aspect. The pedal disc is well developed, though not broader than the diameter of the 

 column. The bodj- is in preserved state cyUndrical, in all specimens considerably higher than broad. The 

 column is more or less wrinkled, in one specimen only in the uppermost part, but forms no tubercles. It is 

 comparatively thin, and the insertions of the mesenteries possibly may be seeu in wholly expanded specimens; 

 traces of indistinct longitudinal furrows also in preserved specimens are sometimes visible. The margin 

 is rather well marked. The tentacles are hexamerously arranged in 6 or 7 cycles, of which the latter is imper- 

 fect and lacking in the smaller specimens. The tentacles are in preserved state wrinkled and devoid of basal 

 thickenings, the inner tentacles are considerably thicker than the outer papilliform ones. No specimen had 

 involved tentacles, and it is a question whether the tentacles may be wholly covered by the column, as the 

 sphincter is comparatively weak, in comparison with the size of the specimens. The oral disc is in contracted 

 state of the animal concave, but not as deeply excavated as in Adinostola callosa, aiidpro\nded with radial 

 furrows, corresponding to the insertions of the mesenteries. The mouth is provided with distinct gonidial tu- 

 bercles. The actinopharynx is one half or one third of the length of the colunm and shows longitudinal ridges, 

 amounting to about 10 in its lower part on each side. The siphonoglyphes are very broad and aborally pro- 

 longated. 



Anatomical description. The ectoderm of the column contains nematocysts, 12 — 19 X 1,5 — 2 /j. 

 in size, and is thin, in comparison to the mesogloea which is of ordinary thickness and less strong than that of 

 A. callosa. It is provided with few protoplasma-poor cells. The endodennal circular muscles of the column 

 are well developed. The sphincter is elongated, reticular, sometimes in several parts with a little tendency 

 to be alveolar; in a specimen I have observed a tendency to stratification not far from the distal end. The 

 sphincter generally much recalls that of Stomphia, though it is less broad. Outside of the sphincter there is a 

 rather thick, sphincter-free part of the mesogloea which, however, does not make out one half of the whole 

 breadth of the mesogloea. The ectoderm of the tentacles is high and contains very numerous spirocysts, from 

 about 22 X 2 to 60 X 4,5 and few nematocysts of typical appearance, from 19 to 27 X 2 — -2,5 /<. There are, 

 besides, also scattered, large specific nematocysts here, from 38 to 52 X 6 — 7 //. Also in this species they vary 

 in number. In one specimen I found onh' a single capsule in the maceration preparations, while in the other 

 specimens they were more numerous, though never common. The mesogloea of the tentacles is tliick and the 

 mesogloeal muscles form rather small but numerous meshes. The mesogloeal radial muscles of the oral disc 

 are reticular, in the outer part of the disc very strong, and interrupted at the insertions of the mesenteries. 

 The ectoderm of the actinopharynx contains sparse, typical nematocysts, 22 — 29 X 2 /t in size, and nemato- 

 cysts with discernible basal part to the spiral thread, 22 — 29 (32) X 4 — 5 (6) /<. 



