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



18. Thesea, Duchassaing and Michelotti, Sujipl. Mem. Corall. des Antilles, p. 12, 

 1864 ; Kolliker, Icones histiologicse, pt. ii. p. 137. 



This genus should probably be included here, as having affinities to Acts. The 

 colony is upright, ramified, with a horny and calcareous axis. The polyps arise from 

 either side of the flattened branches ; they are short. 



19. Acis, Duchassaing and Michelotti, Mem. Corall. des Antilles, p. 19, 1860 ; Suppl. 

 Mem., p. 14, 1864; Kolliker, Icones histiologicse, pt. ii. p. 136, 1865; Pudley, 

 Ann. and Mag. Nat. Hist., ser. 5, vol x. p. 126, 1882. 



The colony is branched, the polyps are small, with wart-like verrucse, usually placed 

 at considei-able intervals on the sides of the main stem and branches. The cceneuchyma 

 is armed with immense spicules in the form of either smooth or warty spindles, those 

 on the stem often reach to a length of from 1 to 3 mm. The polyp spicules are 

 smaller scales or discs. The spicules on the basal portions of the tentacles form an 

 operculum over the retracted polyp. 



20. Elasmogorgia, u. gen. 



Elasma, Wright and Studer, Archiv f. Naturgesch., Jahrg. liii. BJ. i. p. 58 {Elasma having 

 been already utilised for a reptile, Elasmogorgia is substituted). 



A simple or slightly branched colony with thin cceneuchyma. The polyp calyces 

 project as inconspicuous warts. The calyx margins are infolded over the tentacles when 

 retracted, so that the latter appears to be invaginated. The spicules are warty spindles, 

 which lie thickly in the cceneuchyma, forming a uniform layer. 



21. Muricella, Verrill, Trans. Connect. Acad., vol. i. p. 450, 1869. 



The colony is branched, with a thin coenenchyma. The pol5q^:is are short, subconical 

 wart-like and usually arise at right angles from their bases. The spicules of the 

 coenenchyma are long warty spindles ; shorter forms occur in the calyces. 



22. Eumuricea, Verrill, Trans. Connect. Acad., vol. i. p. 449, 1869. 



The colony is branched, the polyps form tubular warts, exhibiting when retracted an 

 eight-rayed figure. The spicules in the coenenchyma and calyces are elongated sharp- 

 pointed spindles. 



