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



5. Ellisella, Gray, Proc. Zool. Soc. Lond., p. 257, 1857; Cat. Lithophytes Brit. 



Mus., p. 25, 1870; emend. Studer, Monatsber. d. k. preuss. Akad. d. Wiss. 

 Berlin, p. 659, 1878. 



The colony is simple or dichotomously branched, with a thick coenenchyma, and 

 slightly developed verrucas, which are disposed in two rows on the axis. The 

 coenenchyma contains both double clubs and spindles. 



6. Verrucella, Milne-Edwards (pars), Hist. Nat. des Coralliaires, t. i. p. 184 ; 



Kolliker, Icones histiologicse, pt. ii. p. 140; Duchassaing and Michelotti, 

 Mem. Corall. des Antilles, p. 33, Suppl. p. 114. 



The colony is branched. The axis is lamellar and calcified. The verrucse are 

 wart-like, on the summits of which the bases of the polyp tentacles form an eight-rayed 

 star-like operculum. The spicules of the coenenchyma are beset with roundish and 

 conical simple warts, there are also double stars, with transitions to double spindles and 

 simple spindles, and there are also minute spiny double stars. 



7. Gorgonella, Valenciennes {pars), Comptes rendus, t. xli. p. 14 ; Milne-Edwards, 



Hist. Nat. des Coralliaires, t. i. p. 183, 1857 ; Valenciennes (pais), Kolliker, 

 Icones histiologicse, pt. ii. p. 139. 



The colony is much branched, in one plane, often forming a network by the 

 anastomosis of the branches. The verrucse are inconspicuous, wart-like, disposed on 

 two sides of the branches. The axis is lamellar, and radially striated. The coenen- 

 chyma includes warty double spheres and double spindles. 



8. Ctenocella, Valenciennes, Comptes rendus, t. xli. p. 14; Milne-Edwards, Hist. 



Nat. des Coralliaires, t. i. p. 185 ; Eidley, Rep. Zool. Coll. H.M.S. " Alert," 

 p. 348. 



The colony is branched in one plane ; and so as that all the simple twigs arise in 

 an ascending order from the upper surface of the stem. The verrucse are short on two 

 sides of the twigs. There are distinct median furrows. The spicules are warty double- 

 clubs; those of the polyp calyces are, according to Ridley, somewhat different from those 

 of the coenenchyma, being longer and provided with two, often three whorls of tubercles. 

 The inner whorls so approach in the middle of the spicules, that the median naked zone 

 which is characteristic of the spicules of the coenenchyma, is here absent. 



