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Show 1906.] ALCYONARIANS F R O M ZANZIBAR. 413 XENIA RIGIDA, sp. n. A small colony 15 m m . in height by 12 in breadth, and 8 in thickness. The polyps are stiff and substantial, about 3*5 m m . in height, with a basal breadth of 3 mm., tapering to 1*75 at the base of the tentacles. The tentacles are 2 m m . long and bear three rows of rounded wart-like pinnules, leaving a triangular bare streak on both surfaces. There are about a dozen pinnules in each longitudinal row. The pinnules appear very closely packed in sloping transverse rows of three. The wdiole surface of polyps and tentacles is thickly covered by minute rod-like spicules (0*06 X 0*08), which produce a somewhat glistening frosted appearance. Besides these there are numerous zoochlorella?. This form resembles X. plicata Schenk in having rounded wart-like pinnules in three rows, but differs in the shape of the tentacles, the number of the pinnules, and the nature of the spicules (round or oval discs in X. plicata). Loccdity. Wasin Channel, 10 fms. HETEROXENIA ELISABETHS Kolliker. A dense cluster of dimorphic polyps borne on a thick stalk about 2*5 centims. in height, and 1 centim. in breadth. The cluster itself has a diameter of 3*5 centims. The living forms were white and grey in colour, and kept the tentacles continually and rapidly opening and closing. The large polyiis are numerous and marked by annulations which are probably due to contraction. They vary from 15- 22 m m . in length, and from 2-2*5 m m . in breadth. The tentacles in the fully matured polyps are from 5*5-6*5 m m . in length, and 0*5 m m . in width. The pinnules are arranged in four rows on each side of the middle line, leaving both on the oral and on the aboral surface a bare strip which stretches the whole length of the tentacle. The pinnules are 0*6-0*9 m m . in length, and from 0*05-0*2 m m. in width. They are all long and slender, with the exception of a few wart-like pinnules at the proximal end. Besides the relatively distant large polyps, the crown bears numerous small individuals which fill up all the gaps. Those on the margin show tentacles with small wart-like pinnules arranged in two rows. In a polyp 2 m m . long the tentacles are 0*8 m m. in length, and show two rows of pinnules on each side with seven pinnules in each row, leaving a narrow bare space on the oral and a broad bare space on the aboral surface. Towards the centre of the crown the majority of the small polyps show no trace of tentacles or pinnules, but exhibit only a slight tendency to be lobed at the margin. These are usually 4*5 m m . in length and have semitransparent walls. Loccdity. Towards Kiungani, just below low tide in a fathom or so of water. Previously recorded from Zanzibar and Port Denison. |