xxxiv THE VOYAGE OF H.M.S. CHALLENGER. 



less porous than that of Briareum. The polyps are not prominent and are scattered. 

 It has extremely characteristic spicules. 



9. Spongioderma, Kolliker, Verh. phys.-med. Ges. Wiirzburg, N. F., Bd. ii. p. 8. 



Solanderia, Mobius, Nova Acta Acad. Cags. Leop., Bd. xxix. Tab. 1, 186L 



{T) Ridley, Rep. Zool. Coll. H.M.S. "Alert," Alcyonaria, p. 351. 

 Homophyton, Gray, Proc. Zool. Soc. Lond., 1866, p. 27. 



In this genus the colony forms a tree-like, branched cylindrical stem, with poljrps 

 retractile into their calyces, and there are distinct longitudinal canals in the periphery of 

 the axis. The spicules are well figured by Dr. Mobius, who has corrected his mistake of 

 describing some siliceous spicules as those of the Alcyonarian. 



10. Iciligorgia, Ridley, Report Zool. Coll. H.M.S. "Alert," Alcyonaria, p. 351 ; 



? Duchassaing, Revue des Zoophytes et des Spongiaires des Antilles (Paris 

 1870), p. 12. 



The colony is upright and branched ; the stem and branches are compressed, 

 irregular in section ; the completely retractile polyps occur in a row within a groove along 

 the sharp edges of the branches. The medullary mass forms an axis of spicules. It is close, 

 but brittle in texture, not penetrated by, but surrounded by, longitudinal canals. While 

 there is no doubt of the genus described by Ridley, it does not seem quite certain if it be 

 the same as that described by Duchassaing. 



Family II. Sclerogorgid^. 

 Sclerogm-giacex, Kolliker, Icones histiologies, pt. ii. p. 142. 



In the representatives of this family a distinct axis is formed of a tissue consisting 

 of numerous closely intercalated elongate spicules with dense horny sheaths. The axis 

 is surrounded by longitudinal canals, into which there open the reticulated coenenchy- 

 matous canals uniting the polyps. The polyps exhibit a wart-like protruding calyx 

 portion, within which the tentacles may be completely retracted. 



In Suberogorgia suberosa (Esp.), the stem and branches are flattened, the polyps arise 

 especially from the narrow margins, while the naked surfaces of the stem and branches 

 exhibit a deep longitudinal groove. Below this latter lie the wide longitudinal canals, 

 one on each side of the axis. These vessels are in communication with the network of 

 canals distributed in the ccenenchyma. 



1. Suherogorgia, Gray. I 2. Kerocides, Wright and Studer. 



