492 SYDNEY J. HICKSON. 



Siphonogorgia inirahilis Klz. (Figs. 11 and 12.) Klunzinger (14) and Kiikenthal (15). 



Two fragments, A, from Suvadiva Atoll, 25 fathoms across the mouth of the passage, B, 

 from Fadifolu Atoll, 70 fathoms outside atoll N.W. on steep slope. 



These two fragments differ in some important particulare from Klunzinger's species and 

 from one another, but it will be more convenient at present to name them Siphonogorgia 

 inirahilis Klz., and to point out the chief points of disagreement ^vith the t^^e specimen than 

 to refer them to a new species. 



Fragment A from Suvadiva may be only a primary branch of a large colony. It is 

 110 mm. in length, with nine branches on one side and five on the other. Only one of these 

 branches shows any tendency to further ramification. 



In specimen B it is possible we have an almost complete specimen with only the base 

 missing. It is 100 mm. in length, and is very much broken up, but some of the longer branches 

 exhibit secondary and even tertiar}' ramification. 



Both of these fragments have a dirty-blackish crust, formed by an epizoic sponge, cover- 

 ing both stem and branches. In specimen B this crust is so thick on many of the branches 

 and a part of the main stem as to completely hide the red colour of the coenenchymal spicules, 

 but in A the red colour can be seen through the sponge, as also in the main stem and some 

 of the branches of B. The sponge belongs to the genus Halisarca, and I am informed by 

 Professor Topsent it probably belongs to the species H. Dujardini. In both specimens antho- 

 codiae can be clearly seen, and are particularly noticeable owing to their bright yellow colour. 



The specimens agree with the original specimen of Siphonogorgia mirabilis in the following 

 particulars. 



The colonies branch in one plane, sometimes dichotomously. The stem and branches are 

 almost cylindrical, the finest branches irregularly angular. The extremities of the finer branches 

 are blunt, and bear from 4 — 6 anthocodiae. The anthocodiae occur on all sides of the branches 

 and twigs, but are scarce on the larger branches, and fail altogether on the lower part of the 

 stem (specimen B). 



The spicules of the coenenchym are spindles covered with warts and knobs, and of a deep 

 red colour. They are irregularly arranged on the main stem and larger branches, but almost 

 parallel with the axes on the smaller branches. The spicules of the anthocodiae are yellow in 

 colour, slender spindles, with sparse warts and tubercles. 



The most important poiut of difference to be observed between the Maldive forms and the 

 tv^e lies in the size of the spicules. According to Klunzinger the largest spicules of the 

 coenenchj-m are 0"5 mm. x 0'128 broad. In the Maldive forms some of the largest spicules are 

 4 mm. X 02 mm., but the average is about 2 mm. x 0'15 mm. The size of these large spicules 

 varies so much in some of the species that it is doubtful whether much reliance can be laid 

 upon the figures given bj' some authors as being by any means exclusive. Kolliker in his 

 original description of Siphonogorgia godeffroyi states that the spicules vary from 1 — 4 mm. in 

 length. In the Challenger series the sizes of these spicules are given by Wright and Studer 

 as follows, S. pallida 2 x -3, S. pustulosa 2 x -38, S. pendula 2'8 x -224, S. Kollikeri 1-2 x 02, 

 and the spicules of Kiikenthal's species were S. cylindrata 3"7 x 0"4, S. miniacea 1'3 x 0'14. 

 It is to be observed, however, that in none of the descriptions of the species these spicules 

 are said to be so small as O'o mm. in length as stated to be the case by Klunzinger in S. mira- 

 bilis. From the fact that Klunzinger's excellent work is unfortunately hampered by many 



