354 COELENTERATA ANTHOZOA chap. 



thin and the zooids imperfectly or not retractile. Ceratoisis, 

 Wright ; Atlantic Ocean, extending from shallow to deep water. 

 The branches arise from the nodes. Chelidonisis, Studer ; deep 

 water off the Azores. Isidella, Gray ; Mediterranean Sea. 

 Bathygorgia, Wright ; off Yokohama, 2300 fatlioms. This genus 

 is unbranched, with very long internodes and short nodes. The 

 zooids are arranged on one side only of the stem. 



Fam. 2. Primnoidae. — This is a well-marked family. The 

 axis of the colonies is horny and calcareous. The coenenchym 

 and the non-retractile zooids are protected by scale-like spicules, 

 which usually overlap and form a complete armour for the pro- 

 tection of the soft parts. On the aboral side of the base of each 

 tentacle there is a specialised scale, and these fit together, when 

 the tentacles are folded over the peristome, to form an operculum. 



The principal genera are : — Primnoa, Lamouroux ; Atlantic 

 Ocean, occurring also in the Norwegian 'fjords. This genus is 

 usually found in moderately deep water, 100 to 500 fathoms. 

 Primnoella, Gray. This genus seems to be confined to the 

 temperate seas of the southern hemisphere. It is unbranched. 

 The zooids are arranged in whorls round the long whip-like 

 stem. Plumarella, Gray; southern hemisphere, in moderately 

 deep water. This is branched pinnately in one plane. The 

 zooids are small and arise at considerable intervals alternately 

 on the sides of the branches. Stenella, Gray ; widely distributed 

 in deep water. The zooids are large and are arranged in whorls 

 of three situated at considerable distances apart. Stachyodes, 

 W. and S. ; Fiji, Kermadecs, Azores, in deep water. Colony 

 feebly branched. Zooids in regular whorls of five. Other 

 genera belonging to this group of Primnoidae are Thouarella, 

 Gray, and Amphilaphis, Antarctic seas. 



The following genera are placed in separate sub-families : — 

 C'al I ozostron, Wright; Antarctic Sea, 1670 fathoms. The axis 

 is procumbent and the zooids are thickly set in rows on its 

 upper surface. . The zooids are protected by large imbricate 

 scales, of which those of tlie last row are continued into long 

 spine-like processes. Ccdyptrophora, Gray ; Pacific Ocean, in 

 deep water. The base of the zooids is protected by two remark- 

 ably large scales. Primnoides, W. and S. ; Southern Ocean. 

 The opercular scales are not distinctly differentiated and the 

 calyx is therefore imperfectly protected. 



