I 27 



My examination of Cephalodiscus has convinced me that the characters of the coenoecium 

 form a reliable means of distinguishing the species in that genus. I am accordingly inclined to 

 think that the specimen of Rhabdopletira from Station 204 is probably a new species, characterised 

 by the small number of tube-rings, by their comparative delicacy and thinness, and by their 

 angular projection to the exterior. The specimen is, however, so fragmentary that I do not 

 consider myself justified in giving it a specific name. It may be hoped that other specimens 

 will hereafter be found among the "Siboga" dredgings which will make it possible to come to 

 a more satisfactory conclusion on this point. There is at present no reason for assuming that 

 the peristomes found have acquired their full number of rings. 



The following comparison of the "Siboga" specimen with Norwegian specimens of R. 

 nonnaui illustrates some of the differences between the two forms ; — 



Rhahdopleura sp. ("Siboga"') 1\ . nonnaui. 



Number of rings of peristome 13 — 15 50 — 60 



Length of peristome '64 — -70 mm. 2-59 — 2'88 mm. 



Diameter of peristome 175 — 210 a. 255 — 270 u.. 



Thickness of wall of peristome, at the middle of a tube-ring. 7"5 — 11 "5 v.. 16 — 24,0.. 



Diameter of pectocaulus 20 — 22 a. 32 a. 



It will be observed that the East Indian form is in all respects smaller than the Norwegian 

 form, while the thickness of the wall of its peristome is distinctly less. 



The following synonymy gives references to some of the more important memoirs dealing 

 with Rhabdoplciira. Other papers, not mentioned here, are referred to by Fowler (92, 2). 



R. norinani Allman. 



R. normani Allman, (Quart. J. Micr. Sci. IX, 1869, p. 58; Rep. Brit. Ass. (Norwich meeting, 

 1868), 1869, p. 311; HiNXKS (80), p. 580, PI. LXXXII, fig.S. I, 2, 4—7; L.VNKESTER (84), 



p. 622, Pis. XXXVII^w— XLI; Fowler (92, i; 92, 2; 04); Norman, Ann. Mag. Nat. Hist. 

 (6) XIII, 1894, p. 131; (7) XII, 1903, p. loi n.; CONTE et Vanev (02, r, 2); Schepotieff (04). 

 R. mirabilis Sars (72); Quart. J. Micr. Sci. XIV, 1874, p. 23. 



R. compacta Hincks. 



R. compacta Hincks (80), p. 58 1, Pi. LXXII, figs. 8, 8rt, 9; Jullien, Bull. Soc. Zool. France, 

 XV, 1890, p. 183. 



R. grivialdii Jullien. 



R. grimaldU Jullien, Bull. Soc. Zool. France, XV, 1890, p. 180; JULLIEN et CaLVET (03), 

 p. 23, PI. I, figs. \a, \b. 



R. Dianjibialis Jullien. 



A', manubialis Jullien et Calvet (03), p. 24, PI. I, fig. 2. 



S. mirabilh appears to be identical with Spongkola Jis/u/aris, described by V. E. Schli.zk in 1S77, and it has been demonstrated by 

 the observations of S. Lo Bia.sco and P. Mayer (Zool. Anz., XIII, 1890, p. 687; of. also Miii,i.Y, Rep. Brit. Ass. (Cardiff, iSgi), 1S92, 

 p. 368) that this is the Scyphistoma form of NausUhoe. Two other species of Stcphanoscyphus are described by Kirki'atrilK (Ann. Maj;. 

 Nat. Hist. (6), V, p. 13), one of them from the China Sea. Nausithoe is recorded by Maas in his account of the Scyphomedusae collected 

 by the ''Siboga"-Expedition (Monogr. XI, 1903, p. 19). 



