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the average length. The total length of the zooecium shown in fig. 5 is 1360 a. The length of 

 the narrow part of the proximal zooecium in tig. 4, measured to the level of the proximal lateral 

 diaphragm, is 600 u. ; and that of the broad part of the zooecium, from the same diaphragm, 

 is 1030 u.. The total length of the distal zooecium in the same figure is 1250 u,, while that 

 of the short zooecium shown in fig. 3 does not exceed 700 u., measured to the distal end of 

 the adhen-nt part. The zooecia are usually about 500 u in greatest breadth, and the diameter 

 of the narrow proximal portion is about 50 u. 



A. fibrosum has been recorded by Miss Thornelv l ), without description, from the Gulf 

 of Manaar. 



Arachnoidea 2 ) J. E. S. Mooie. 



Arachnoidia Moore, 1903, "The Tanganyika Problem", p. 297, text-fig. on p. 296. 

 Araclinoidia Rousselet, 1907, "Zool. Res. Third Tanganyika Exp.", Proc. Zool. Soc, p. 255, 



PI. XIV, figs 5, 6. 

 Arachnoidea Annandale, 191 1, Ree. Ind. Mus., VI, p. 19S. 



1. Arachnoidea protecta n. sp. (PI. III, figs 7 — 11). 



378. E. Stat. 71. Makassar, o — 32 Metres ; mud, sand with mud, coral. 



Zooecia discrete, relatively large, surrounded at their edges by irregular processes. Mode of 

 branching as in Arachnidium. Orifice borne on a long peristome, with thick chitinous walls, strongly 

 quadrangular when the polypide is retracted. Collar unusually large. Tentacles not less than 16. 



The genus Arachnoidea was described by Moore (1903) from about 20 fathoms in Lake 

 Tanganyika, the single species found being designated A. ray-lankesteri. A later description 

 of the same species, also from Tanganyika material, has been given by Rousselet (1907). 

 Annandale (loc. cit.) has referred it to the Fam. Hislopiidae. LorPENS 3 ) considers Arachnoidea 

 inseparable from Arachnidium. 



The occurrence of a marine species which can be referred to Moore's genus seems to 

 me of particular interest. But the resemblances between the •Siboga' specimen and those from 

 Lake Tanganyika are too striking to be overlooked ; and I feel no doubt that the forms from 

 the two localities must be placed in the same genus. As Moore pointed out, Arachnoidea closely 

 resembles Arachnidiuin in its general characters; but I think he was justified in separating it 

 from this genus by reason of the character of the peristome. In Arachnidium this part forms 

 a rounded mammilla, as shown in figs 3 — 6, referring to A. irregularc. Hincks accordingly 

 compared the genus with an Alcyonidium having discrete zooecia. In Arachnoidea, on the 

 contrary, the part in question is much elongated. lts wall is protected by a chitinous layer 

 which shows no tracé of the circular annulations in a relatively soft cuticle which were found 

 in the preceding species. In the retracted state, the peristome is quadrangular, the actual orifice 

 being perfectly square (fig. 11). It is true that in Arachnidium fibrosum Hincks 4 ), the distal 



1) Tiioknki.y, L. R., 1905, p. 127. 



2) The name as originally introduced is Arachnoidia. I propöse to regard thi^ as a lapsus calami for Arachnoidea. 



3) Loppens, K., 190S, "Bry d'Eau dovtce", Ann. Biol. lacustre, III, pp. 150, 154, 174. 



4) Hincks, T., 1880, p. 511. 



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