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



of a slender form of Paramuricea. This has also caused later investigators to include 

 Villogorgia nigrescens amongst the Muriceidae. 



Kidley gives the name Villogorgia the priority over Paramuricea, and takes 

 Villogorgia nigrescens as the type of the species of Paramuricea as definitely charac- 

 terised by KoUiker. 



An examination of the type specimen of the species described by Duchassaing and 

 Michelotti establishes beyond a doubt that it is a true Muriceid. The branches, which 

 are borne on a horny axis of a dark-brown colour, have the polyps cylindrical in shape, 

 placed perpendicularly thereon ; the polyp calyx, when retracted, is sunk down below 

 the basal portions of the tentacles, which then form a low conical operculum. The 

 coenenchyma is thin, and armed with spicules, which are not closely crowded together, 

 but are separated from one another by naked portions of the coenench5rma. 



The polyp calyx on the other hand appears thickly filled with spicules. The 

 spicules of the coenenchyma are four-, six-, or eight-rayed stars ; in the polyp bodies 

 there are for the most part tripartite spicules which are placed closely together, and 

 the points of which interlock. The tentacular portion, which is very deeply drawn in, 

 has at its base a colleret consisting of curved spiny spindles, placed as a ring upon 

 which the tentacular operculum rests. This operculum is so formed that the portion of 

 the tentacles which is not infolded is furnished with a series of two curved spicules, 

 coiiverging upwards ; a third spicule is placed at the basal portion of the operculum, 

 between the fork thus formed. The structure, it will be seen, differs in many important 

 details from the diagnosis of the genus as given by Duchassaing and Michelotti ; still 

 the species cannot be placed in the genus Paramuricea of Kolliker, although no doubt 

 there is a near relationship. The chief differences lie in the form of the spicules of 

 the coenenchyma, and especially in the structure of the tentacular operculum. In 

 Paramuricea a larger portion of the basal portions of the tentacles form the opercular 

 covering, and this is covered with whole rows of spicules placed en chevron. As 

 nearly related forms there may be reckoned, as Ridley has rightly done, Brandella 

 intricata, Gray ; Paramuricea gracilis, Studer ; Villogorgia mauritiensis, Ridley ; 

 and perhaps Boarella Jlahellata, Gray. Emended, the diagnosis of tlie genus may 

 stand as follows: — 



A Muriceid with a horny axis and a thin coenenchyma ; the polyps are cylindrical 

 in shape, and placed perpendicularly on the stem. The tentacular operculum is shallow 

 and conical ; the spicules of the coenenchyma are partly four- to eight-rayed stars, 

 occasionally mixed with spindles. The polyp spicules are " Stachelplatten " and tri- 

 partite spindles. The basal portions of the tentacles which form the opercular covering 

 contain a series of two spicules, converging to the apex, between which there is an odd 

 intermediate spicule. There is always a ring-shaped colleret of spicules below the 

 tentacles. 



