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



Subfamily 3. Primnoidin^, n. subfam. 



Colony branched, with opjsositely placed polyps. The spicules are flat, thin scales, 

 deposited uniformly in the coenenchyma and in the polyp calyces, and covering each 

 other like tiles on a roof. The opercular scales are pot distinctly differentiated and 

 therefore the oral region is only incompletely protected. The axis is horny, calcareous. 



Genus Primnoides, n. gen. 



An upright colony ramified in one plane, the branches arise oppositely and bear two 

 rows of oppositely placed polyps. The spicules on the stem and calyces are flat, thin 

 scales, which cover each other like roof tiles and are uniformly spread over the stem 

 and calyces. The operculum is rudimentary and not capable of covering the mouth 

 of the retracted polyp. Axis horny, calcareous. The polyps arise in an intercalary 

 manner. 



This peculiar form constitutes a type which differs from all other Primnoids in 

 that a differentiation of the calcareous bodies into scales of the coenenchyma, of the 

 calyx, and of its operculum has not as yet taken place, or no longer occurs. The 

 uniformly developed scales are, however, formed as in other Primnoids and are closely 

 related to those of Plumarella. They are flat, thin, with a central nucleus surrounded 

 l)y little prominences. The free projecting edge is convex, smooth and entire, the 

 covered edge straight, thickened, and provided with teeth and spines. On the stem 

 and branches the direction of the scales is usually towards the apex, where two calyces 

 arise their direction deviates from the middle line towards the mouths of the calyces. 

 At the oral region are found six to eight slightly projecting scales, which, however, do not 

 form a proper operculum, and are not cajjable of closing the mouth in the contracted 

 calyces. The axis is hard, horny, calcareous, only in the thinner twigs flexible and soft. 

 Growth takes place as in Primnoella, Caligorgia, and others. New jiolyps arise in 

 the interstices between the old ones, but always at some distance from the bases of the 

 two polyps. 



Primnoides sertularoides, n. sp. (PI. XIX. fig. 1, la; PI. XXI. fig. 16). 



The upright, straight stem gives off opposite branches on two sides ; the branches 

 in most cases remain simple, and only exceptionally give off' secondary branches in the 

 same manner. The polyps arise oppositely from the stem and twigs at intervals of 

 2 mm. The calyces are wart-like, 1 to 1'5 mm. long, laterally compressed. They 

 arise from the stem with a broad base and diminish towards the apex. The scales 



