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



several variously shaped, root-like masses, by which the colony is fixed in the mud, or disc- 

 like, when attached to rocks. The coenenchyma is either membranous or thin, in some 

 species without spicules, in others with either small^ oblong, scale-like spicules, or these 

 intermixed with larger fusiform or club-shaped spicules. The polyps are prominent, with 

 imperfectly retractile tentacles ; the bodies of the polyps are more or less densely covered 

 with fusiform or club-shaped spicules, of which in some species a certain number project 

 beyond the base of the tentacles and form a defensive calyx. The tentacles are covered 

 with spicules, which when the tentacles are partially infolded serve as an opercular 

 covering. 



This subfamily contains the following genera : — 



1. Ceratoisis, Perceval Wright. — Stem simple or branched. Branches when 



present arising from the calcareous joints. Spicules fusiform. 



2. Acanella, Gray {emend). — Stem branched. Branches arising from the horny 



joints. Spicules fusiform. 



3. Lepidisis, Verrill. — Branches from horny joints. Spicules fusiform and 



lenticular. 



4. Batliygorgia, n. gen. — Stem simple. Spicules biclavate. 



Genus 1. Ceratoisis, Perceval Wright. 



Kerafoisis, E. Perceval "Wright, Ann. and Mag. Nat. Hist., December 1868, p. 427; January 1869, p. 23. 



„ J. E. Gray, Cat. Lithophytes Brit. Muo., July 1870, p. 18. 



„ Th. Stiider, Monatsber. d. k. preuss. Akad. d. Wiss. Berlin, October 1878, p. 662. 



Ceratoisis, Verrill, Bull. Mus. Comp. Zool., vol. xi. p. 10, July 1883. 

 Lepidisis, Verrill (pars), loc. cit., pp. 10, 18. 



Axis simple or feebly branched, when branched, the branches proceeding from the 

 calcareous internodes. The internodes are in a young state hollow in most, getting 

 nearly solid by age, but in some apparently remaining as a thin tube of calcareous 

 material, smooth or fluted. Either rooted in the mud by rhizome-like processes or to 

 rocks by a disc-like attachment. Polyps arranged on the axis either irregularly, in 

 verticles, or in a uniserial manner ; prominent ; the tentacles imperfectly retractile. 

 The coenenchyma is membranous or thin ; sometimes without spicules, but more 

 frequently with either small oblong (lenticular) or large fusiform spicules, or with both. 

 The spicules on the bodies of the polyps either lenticular or fusiform, eight large fusiform 

 spicules starting from below the base of the tentacles forming a defensive calyx. 



The lenticular or oblong scale-like form of spicule occurs in Ceratoisis grayii, E. 

 P. W., the type form of the genus, and this form of spicule occurs also greatly developed 

 in Ceratoisis grandiflora, Th. Std.; so that it would seem impossible to distinguish 

 between the unbranched species of the genus Lepidisis, Verrill, and the unbranched 



