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



times coalesce and sometimes are free. The coenenchyma forms a continuous sheath 

 over the whole axis and its ramifications, so that the colony has a leaf-like appearance. 

 The polyps are scattered over the face of the expanded folia, not seated on their edges. 



The longitudinal canals follow in the course of the ramifications of the axis, while 

 the polyps in the leaf-like coenenchymatous extension communicate with each other 

 by a reticulated canal-system, which finally opens into the longitudinal canals. 



12. Phycogorgia, Valenciennes, Comptes rendus, t. xli. p. 13 ; Milne-Edwards, Hist. 

 Nat. des Coralliaires, t. i. p. 182; Verrill, Trans. Connect. Acad., vol. xlviii. 

 p. 413. 



The colony is ramified, with a horny axis dividing into a number of thin leaf -like 

 expansions, which are covered with a thin coenenchyma. The polyp openings are sunk 

 within the coenenchyma. 



Family XL Gorgonellid^. 



Gcn'gonellacex, Valenciennes, Comptes rendus, t. xli. p. 14 j Milne-Edwards, Hist. Nat. des 



Coralliaires, t. i. p. 182 ; KoUiker (pars), Icones histiologies;, pt. ii. p. 140. 

 Elliselladx, Calligorgiadx {pars), Gray, Cat. Lithophytes Brit. Mus., pp. 24, 34. 



In the species of this family the coenenchyma is thin, smooth on the surface, with 

 small spicules in the form of warty double-clubs and stellate forms. The polyps have 

 more or less well-developed verrucse, and are usually biradially disposed. The axis is 

 lamellar and calcareous, but retains its shape after the extraction of the calcareous matter. 



The family Gorgonellidse is here accepted as diagnosed by Kolliker, the genus 

 Herophila, Steenstrup (Riisea, D. and M.), being, however, excluded. 



The colonies in GorgonellidEe form simple or branched masses whose calcareous 

 axis gives to the whole a rigid appearance. The branches and twigs are frequently 

 flattened and the polyps are either distributed in two rows on the edges thereof, or 

 are so disposed in lateral bands that a free space is left in the middle, in which are to 

 be found one or more longitudinal furrows. The longitudinal canals are partly of small 

 diameter, partly large. Two usually occur on the surfaces of the stem which are destitute 

 of polyps. On the surface of the coenenchyma in dried specimens their position is marked 

 by longitudinal grooves. 



Gray divided this family into a large number of genera and arranged these in 

 subfamilies. The majority he included within his family Elliselladas, while others, 

 Nicella and Scirpearia, are referred by him to the entirely heterogeneous family of 

 the Calligorgiadse. The genus Hypnogorgia, Duch. and Mich., which Gray refers to the 

 EUiselladae, is most probably a Muriceid, as seems apparent from the representation ^ and 



' Suppl. Coral des Antilles, pi. v. p. 1. 



