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Show 1906.j ALCYONARIANS FROM ZANZIBAR. 439 The stalk has a plump smooth appearance, but there are numerous small spicules in the cortical layer. The number of pinnules on each side is 46, but of these five on one side and seven on the other, situated at the top of the stalk, are rudimentary. The metarachidial surface shows a bare streak 3-4 m m . in breadth, loosely overlapped by the pinnules in its middle region. There is no visible zooid streak, but the surface is not very well preserved. The prorachidial surface is smooth, and seems more deeply coloured than the rest; it varies in breadth from 3*5- 10 m m . The rachis ends bluntly in a small bare area. In the other specimen the axis is exposed ; it tapers rapidly to a fine point, and is soft and coiled for the last 14 m m. The pinnules are somewhat reniform, with a narrow insertion. Thus, on one of the largest pinnules the insertion-line is only 4*5 mm. in length, but the outer margin is at least double. There seems to be some irregularity in the number of the supporting calcareous rays, but in some of the pinnules 4-6 are very distinct and project for about 1*5 m m . The specimen seems to have been somewhat battered, and no importance can be attached to the absence of rays in many of the pinnules. The zooid-plate is basal and strongly developed. It extends in some about halfway up the pinnule ; it is ridged and has an undulatory upper margin. The polyps occur in three or four rows on each side of the margin of the pinnule, occupying a zone about 1*75 m m . in breadth. The spicules of the cortical layer of the stalk consist of small rods and irregularly-branched forms. The following measurements in millims. were taken :- Rods:-0*2x0*03. Branched forms :-0*25 x 0*175 ; 0*3 x 0*175. Locality. Wasin Channel, 8 fathoms. PTEROEIDES PULCHELLUM, sp. n. (Plate XXVII. figs. 1 k 2.) A beautiful finely-preserved colony, 37 m m . in total length and 13 m m . in breadth. The stalk is 16 m m . in length and 2*5 m m . in average breadth. There are 15 (and 16) pinnules, of which 4 (and 5) at the base are very small. Each pinnule is supported by four rays of spicules, which may project about 2 m m . There are about 30 polyps arranged on the margin in a sinuous line, occasionally with young forms a little way down on either surface. The contracted polyps are barrel-shaped, with distinct longitudinal ridges, and the densely-crowded calices seem to differ much as to the depth of the indentation between them. A common height of calyx is 1 mm.; the expanded tentacles are 0*75 m m . in length and their tips enclose a circle about 1 m m . in diameter. There is a prominent oral cone and a circular mouth-aperture. In some polyps the tentacles are pure white ; in others they are backed by a chocolate-brown colour with a hint of blue. This colour is also seen in the calices and on the rachis, especially on its upper region. |