REPORT ON THE ALCYONARIA, 25 



as the family Isidse as now understood ; this unnamed division of Gray's contains his 

 four families of Mopseadae, Acanelladse, Keratoisidae, and Isidae. Verrill makes his 

 family Ceratoisidae include Mopseadse of Gray, but makes no reference to the species of 

 the genus Mopsea, which for reasons given further on seem to be well and easily 

 distinguished from the forms otherwise included in the Ceratoisidae. It has therefore 

 appeared better to make the family, to which we give Lamouroux's name, include the 

 following subfamilies. It may be diagnosed thus : — 



Colony consisting of a simple or branched axis. The axis consists of calcareous and 

 horny (internodal and nodal) regions ; the branches when present arising from either the 

 nodal or internodal regions, sometimes anastomosing ; the axis solid or hollow, smooth, 

 fluted or echinulate. The base of the axis calcareous and attached. 



The ccenenchyma varies greatly, being either very thick {Isis) or forming a thin mem- 

 branous covering as in some species of Acanella, Primnoisis, &c. The spicules are 

 either fusiform, scale-like, or of a six-rayed stellate form. 



The pol}^s are scattered over the main stem or branches, rarely unilaterally 

 arranged ; they are for the most part prominent, though in the genus Isis they are 

 retractile within the ccenenchyma ; in those with prominent polyps the polyp bodies are 

 more or less densely covered with spicules, some of which often project and form a 

 " calyx " round the oral region of the polyp ; the polyp tentacles are externally covered 

 with spicules, they are only very imperfectly retractile, but when folding over the oral 

 region they constitute a quasi- opercular covering somewhat as in the Dasygorgidae. 



( 1. Ceratoisidinae. — Spicules fusiform. 



Subfamilies \ 2. Mopseinae. — Spicules scale-like. 



3. Isidinae. — Spicules hexradiate-stellate. 



Subfamily 1. Ceratoisidin^. 



Keratoisidae, Gray, Cat. Lithophytes Brit. Mus., 1870, p. 18. 



Acanelladx, Gray, loc. cit., p. 16. 



Mqpseadx (pars). Gray, loc. cit., p. 13. 



Ceratoisidx, Verrill, Bull. Mus. Comp. Zool., vol. xi. p. 9, July 1883. 



This subfamily is established for those species of Isidae with prominent polyps and 

 fusiform or club-shaped spicules. 



The axis may be simple or branched, and is made up of calcareous internodal and 

 horny nodal regions. The former are often hollow, more especially in the apical regions 

 of the main stem or its branches. 



Branches when present either arise from the internodal (Ceratoisis) or from the 

 nodal (Acanella) regions. The base of the axis is calcareous, and is either divided into 



(zool. CHALL. EXP. PART LXIV. — 1887.) Sss 4 



