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Show 1906.] ALCYONARIANS FROM ZANZIBAR. 411 diameter of 11 mm.; the polyps are 9-15 m m . in length, 1*2- 2 m m . in breadth, with tentacles 6*5-8 m m . in length and 1*5 m m . in breadth. A few young polyps are present among the older polyps, and have an average length of 1*9 m m . and an average width of 0*5 m m . On their small tentacles, however, from 6-7 pairs of pinnules may be seen. The tentacles in the older polyps are long and slender, with the middle line free throughout its entire length on the aboral surface. The long and slender pinnules are arranged in 2 3 rows on either side of the middle line. Between 30 and 40 were counted on one row. There are abundant calcareous corpuscles of minute size. Numerous zoochlorellre are also present throughout. X. umbellata appears to be a very variable species if we extend it to include those forms with not more than 3 rows of very long and numerous pinnules, with tongue-like flattened free axis. In another specimen the polyps were from 5-11 m m . in length by 1*5 m m . in breadth, with thin transparent walls, with spherical calcareous bodies. The tentacles are long in comparison to the length of the polyp, for they vary from 6*5-7 m m . in a polyp which measures 11 mm., and they may be even longer than the polyps. The long and slender pinnules (1*4 m m . long by 0*15 m m . wide) are arranged in two or three rows on either side of the middle line, leaving on both surfaces a free space which runs the whole length of the tentacle, and giving a fine feather-like appearance to the tentacle. In the younger polyps, which measure about 3*3 nun. in height, the tentacles reach a length of 2*3 mm., and have the pinnules arranged in 3 rows, in the outermost of which there are from 7-9 pinnules. There are numerous spherical zoochlorella?. Another set of specimens (from Chuaka, E. Zanzibar) were characterised by the very long polyps (12-25 mm.), the flatness of the tentacles, and the delicate triangular pinnules in five rows proxi-mally and three rows distally with 24-26 in each row. Another specimen, which when living was white with yellow-brown tentacles, was found growing over nullipore branches. The stalk is firm and has an average length of 11 mm., and an average breadth at the upper end of 4 m m . The polyps are thin-walled and transparent, thickly placed on the crown, from 5-6 m m . in length, with an average width of 0*8 m m . The tentacles are very feathery in appearance, and vary in length from 2-3*2 mm., and have a maximum diameter of 1 m m . The pinnules are arranged in four rows on each side of the middle line, leaving a free space on both the oral and the aboral surface. In the outer row of pinnules the number varies from 14-18, but 17 is the commonest number. There are very numerous zoochlorellae with a diameter of about 0*01 mm., and there are also calcareous corpuscles. Locality. Wasin Channel, 10 fathoms; previously recorded from N e w Britain and from the Red Sea. |