1906.] ALCYONARIANS FROM ZANZIBAR. 411 



diameter of 11 mm.; the polyps are 9-15 mm. iu length, 1-2- 

 2 mm. in breadth, with tentacles 6-5-8 mm. in length and 1-5 mm. 

 in breadth. A few young polyps are present among the older 

 polyps, and have an average length of 1*9 mm. and an average 

 width of 0-5 mm. 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. Thei-e are abundant calcaieous corpuscles of minute size. 

 Numerous zoochlorellse are also present throughout. 



X. umhellata appeai-s to be a very variable species if we extend 

 it to include those foi-ms with not moi'O than 3 i-ows of vejy long 

 and numerous pinnules, with tongue-like flattened free axis. 



In another specimen the polyps were from 5-11 mm. in length 

 by 1-5 mm. in breadth, with thin transparent walls, with spherical 

 calcareous bodies. The tentacles are long in compai/ison to the 

 length of the polyp, for they vary from 6-5-7 mm. in a polyp which 

 measures 11 mm., and they may be even longer than the polyps. 



The long and slender pinnules (1-4 mm. long by 0-15 mm. wide) 

 are arranged in tivo 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 mm. 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 ai-e nianerous spherical zoochlorellaj. 



Another set of specimens (fi-om Ohuaka, E. Zanzibar) were 

 characterised by the A^ery long i^olyps (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 wath 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 mm. The polyps are thin- 

 walled and transparent, thickly placed on the crown, from 5-6 mm. 

 in length, with an average width of 0-8 mm. The tentacles are 

 very feathery in appearance, and vary in length from 2-3*2 mm., 

 and have a maximum diameter of 1 mm. 



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 zoochlorellse with a diameter of 

 about 0-01 mm., and there are also calcareous corpuscles. 



Locality. Wasin Channel, 10 fathoms ; previovTsly recorded 

 from New Britain and fi-om the Red Sea. 



