ACTINIARIA Qc 



Acthelmis schaudinnii n. sp. 



Diagnosis: Column thicker and more robust than in A.intestinalis, and, according to the different 

 state of contraction, cyHndrical or oval. Column not divisible into distinct regions. Typical nematocysts 

 of the column 14 X 2 /i, those of the tentacles 22 — 26 x 2 — 4 fi, those of the actinopharynx 20 — 23 X 

 1,5 — 2 /i. Nematocysts with indistinct basal part to the spiral thread, widened in their basal end, in the ten- 

 tacles 24 — 26 X 1,5 — 2 /<, in the actinopharynx 24 — 29 (36) X 5 — (6) /.<. Number of tentacles about 34. Lon- 

 gitudinal muscles of the tentacles weak. Siphonoplyphes? Pairs of mesenteries 6 + 6 + an imperfect third 

 cycle ; the folds of the pennons high and rather much ramificated, more numerous than the former species, 

 in the reproductive region about 20 — 30. Insertions of the lamellar part of the mesenteries as in A . intesti- 

 nalis. Parietal muscles weak with large, not numerous, low folds. Mesogloea in the region of the parietal 

 muscles thick. Expansion of the parietal muscles as in the former species. Muscles of the mesenteries of the 

 second cycle, although stronger, recalling the parietal muscles of the first cycle. 



Colour? 



Dimensions: Species from Great fiord: length 1,3 cm, largest breadth 0,6cm, length of the ten- 

 tacles about 0,3 cm. — A specimen from New-Zembla: length 0,8 cm, breadth 0,5 cm. 



Occurrence: Spitzbergen. Great fiord Cape Blanck 77°49' N. 20°3' E. 65 m (Romer «& Schau- 



dinn 1898) i sp. 

 New-Zembla Besimennaja Ba^^ clay, 4 — 5 fms. (Nordenskiold-Exp. 1875) 4 sp. 



Exterior aspect: All the specimens were more or less contracted, the proximal as well as the distal 

 ends were drawn in. According to the state of contraction the individuals were cylindrical or more fusiform, 

 the diameter in proportion to the length is, however, in tliis species considerably larger than in A. intcsti- 

 nalis. The column does not seem to be divisible into regions, and its surface is smooth. The insertions of the 

 mesenteries were rather distinct and corresponding to weak longitudinal furrows on the column, which are 

 conspicuous on the involved distal part. The number of tentacles in the specimen from Great fiord was 34. 

 The tentacles were hexamerously arranged and short, as in the former species. The oral disc is inconsider- 

 able. The actinopharynx is of about twice the length of the tentacles, and longitudinally and transversely 

 sulcated. I cannot with certainty decide whether siphonogl5^hes are present or not, they are, at all events, 

 weakly developed, if present, and form no aboral prolongations. 



Anatomical description: The ectoderm of the column is provided with scattered nematocysts, 

 partly typical, always of equal breadth and about 14 X 2 /.( in size, partly widened in the basal end and larger, 

 24 — 26 X 5 /^ ; the ectoderm also contains very numerous mucus-cells. The ectoderm is thicker than the 

 mesogloea, especially in the specimens from New-Zembla. The endodermal circular muscles of the column 

 are weak and form no sphincter. The longitudinal muscles of the tentacles are weak and endodermal, the 

 nematocysts of the ectoderm are 22—26 X 1,5—4 ," i" size, — the breadth variates considerably, so that 

 it is probable that there are two different sizes of capsules. The spirocysts are unto 30 (36) fi long. The radial 

 muscles of the oral disc are weak. The ectoderm of the actinopharynx is high, with numerous nematocysts. 

 The straight, riblike nematocysts, reaching a size of 22 — 24 X almost 2 /i, are the most numerous, those 

 which are a little widened in the basal end and show a small, discernible basal part to the spiral thread, are 



