xlvi THE VOYAGE OF 11. M.S. CHALLENGER. 



The ccenenchyma contains a superficial layer of scale-like calcareous bodies, which arc 

 continued upwards over the calyx, where they are arranged in regular sequence, usually 

 bilaterally symmetrical, they overlap each other around the margin of the calyx ; eight of 

 the scales form an operculum, and they may be brought together so as to close the 

 opening. The calyces are movable ; they are thrust outwards when erect, or are when 

 retracted turned towards the stem, so as to lay their oral apertures against the stem. 

 In some species this retraction is also accompanied by a twisting of the base of the calyx, 

 which turns the oral aperture downwards. 



The Primnoida3 are a well-marked family, without any close relationship with the 

 Muriceidse with which they have been usually united. The opercula which close the 

 cal)^ces of the Muriceida; arc formed of the spicular bases of the tentacles, while in the 

 Primnoidse they are portions of the calyx. The nearest relationship of the Primnoidse 

 seems to be witli certain forms of Chrysorgoroinse. 



J DO 



The Primnoidse may be divided into the foUowino; four subfamilies and wnera : — 



Subfamily I. Callozostrin^. 



1. Calloiostroii, Perceval AVright. 



Subfamily 2. CalyptrophoriNjE. 



2. Calyptrophora, Gray, emend. 



Subfctmily 3. Primnoin^. 



3. Primnoc, Lamouroux. ! 7. Thoziarella , Gray, emend. 



4. Stachyodes, AVright and Studer. ! 8. Amphilaphif^, Wright and Studer. 



5. Calypterinua, AVright and Studer. i 9. Plumarella, Gray, emend. 



6. Stcnella, Gray. i 10. Primnoella, Gray, emend. Studer. 



11. Caligorgia, Gray, emend. Studer. 



Subfamily 4. Primnoidin^. 



12. Primiioides, Wright and Studer. 



Subfamily 1. Callozostrin^. 



The colony consists of a probably creeping stem, which is either attached or free, a 

 point which cannot be decided on the single specimen which is the representative of this 

 subfamily. The axis is feebly calcareous and flexible. The elongated polyps are 

 cylindrical, and arranged in rows ; they arise thickly on the entire stem, except along 

 one longitudinal surface which may be described as the ventral colonial groove, and 



