REPORT ON THE ALCYONARIA. 93 



The presumed relationship of the Muriceidse with the Prinmoidse rests moreover 

 on a purely external resemblance. In both there are large surface spicules and 

 opercular coverings, which latter can more or less close over the mouth. In the one 

 group, however, the operculum is formed by the spicules at the base of the tentacles, 

 in the other by those of the body edge. The formation of the polyps is also different 

 in the two groups. The polyps in the Muriceidse are retractile, but the amount of the 

 retractability differs much. In Acanthogorgia the contraction of the polj^ps and the 

 arrangement for the protection of the soft parts is still very imperfect (and somewhat as 

 in the Ceratoisidae); through Muricea they show affinities to the Plexauridse; and 

 through Elasmogorgia and Muricella with the Gorgouidse. 



The following fourteen genera occur in the Challenger collection. They may be 

 arranged thus : — first, the forms with but slightly contracted tentacles ; then those 

 where the whole crown of tentacles can be concealed within the body. 



Acanthogorgia, Gray. 



Paramuricea, KoUiker. 



Anthomuricea, n. gen. 



Muriceides, n. gen. 



Clemafissa, n. gen. 



Villogorgia, Duch. and Mich, {emend.). 



Echinomuricea, VerriU. 



Placogorgia, n. gen. 

 Acamptogorgia, n. gen. 

 Echinogorgia, Kolliker. 

 Acis, Duch. and Mich. 

 Muricella, VerriU. 

 Elasmogorgia, n. gen. 

 Muricea, Auct. 



Genus 1. Acanthogorgia, Gray. 



Acanthogorgia, Gtslj, Proc. Zool. Soc. Lond., 1857, p. 128. 



„ VerriU, Bull. Mus. Comp. ZobL, vol. xi. No. 1, fig. 30. 



Blepharogorgia, Duch. et Mich., Supp. M^m. Corall. des Antilles, 1864-66, p. 109. 



The genus Acanthogorgia is here taken in the emended sense of VerriU {loc. cit). 

 VerriU includes in the genus Blepharogorgia, Duch. and Mich., but excludes the species 

 Acanthogorgia grayi, Acanthogorgia atlantica, John., and Acanthogorgia hirta, Pourt., 

 which according to their spicules are to be placed in Paramuricea, KoU. ; Acanthogorgia 

 johnsoni, Studer, also belongs to Paramuricea. The following must be added to VerrUl's 

 characteristics with reference to the polyps and spicules. The polyps are elongated, 

 cylindrical, expanded towards the mouth. The anterior part of the polyp is slightly 

 retractUe ; in repose the tentacles bend together inwards over the mouth and are 

 protected by spicules on their dorsal sides. The spicules are spindle-shaped and provided 

 with spines, generally somewhat bent. They form eight longitudinal rows on the body of 

 the polyp, the eight rows being arranged in pairs in a like manner, and the spicules of each 

 paired row are at acute angles with each other. Towards the base of the tentacle the 



