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'I Stat. 27;. Oft" Pulu Jedan, E. coast of Aru Islands, 13 Metres; sand and shells. 

 544. A. ) / ° J J 



^ '[ Stat. 274. 5°28'.2S., I34°53'.9E., 57 Metres; sand and shells, stones. 



126. A.) 



} Stat. 164. i°42.sS., I30°4/.5E., 32 Metres; sand, small stones and shells. 



(sp. ?) 67. C. Stat. 99. Anchorage oft" N. Ubian, 16 — 23 Metres; Lithothamnion-bottom. 



also the following specimens, in the Mus. Zool., Cambridge : — 



'°°' | Torres Straits, A. C. Haddon ColL Reg. Feb. 24, 1898. 



T. S. 100. 

 T. S. 2c 



Queensland, Holborn Island, Port Denison. From the remains of W. A. Haswell's Coll., 

 pres. by the Australian Mus., Reg. Oct. 23, 1899. 



Zoarium large, erect, well branched, reaching a length of at least 132 mm. Stem thick 

 at its base, where it is strengthened by rootlets given off at various points, the vvhole comrflex 

 here reaching a thickness of 10 mm. The ordinary internodes, without the addition of rootlets, 

 measure about 400 — 550 u. in diameter. Zooecia biserial, arranged in an open spiral curving 

 round the stem, a considerable part of which is exposed. Each group of zooecia forms, as a rule, 

 from i 1 /.-, to 2 complete turns of the spiral, seldom as many as 2 l /. 2 turns. A thick diaphragm 

 typically occurs at the distal end of each group of zooecia, a short interval separating the group 

 from its successor. In branches which have reached the limit of their growth a spiral series 

 may be broken up into several separate groups, each of a few pairs of zooecia, and isolated 

 from one another by a considerable interval of bare stem. A branch is given off, on one side 

 only, immediately on the proximal side of a stem-diaphragm ; successive branches being alternate 

 and on opposite sides of the stem. The zooecia are completely connate along their whole length 

 when the kamptoderm is fully invaginated, and the edge of the entire series then forms an 

 angular groove, the deepest part of which corresponds with the line separating the two series- 

 of zooecia, the outer walls of which project so as to form two sharp ridges bounding the 

 groove. The oral wall of the zooecium thus slopes downwards into the groove; and the orifice 

 is situated on the distal part of the flat surface so constituted. In transverse section the 

 zooecium is much broader than long, and the basal attachment to the stem is thus oblong, 

 the two longer sides being the proximal and distal ones, the two series usually interdigitating. 

 Polypides with 8 tentacles and a gizzard. 



The present species, which has a considerable resemblance to the Mediterranean A. semi- 

 convoluta Lamx, as figured by Heller x ), is a robust one, and is characterised by possessing 

 a nearly continuous spiral of zooecia, which is, however, broken up into groups by distinct 

 intervals. The spiral is arranged in such a way as to leave a considerable part of the thick 

 stem exposed to view. The stem is divided by stout diaphragms, perforated at their centre, 

 into internodes, each of which corresponds with a single group of zooecia. In rare instances a 

 diaphragm may fail to develop. The specimen 198. A. appears at first sight to have unusually 

 long internodes, since an interval of as much as 65 mm. may occur between two successive 



1) Heller, C, 1867. "Bry. Adriat. Meeres", Verh. k. k. zool. -bot. Ges., XVII, p. 127, PI. V, figs 1, 2. 



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SIBOGA-EXPEDITIE XXVlIIa. 



