714 PROCEEDINGS OF THE NATIONAL MUSEUM. vol. xxxv. 



Family RENILLID^. 



Rachis expanded into a flattened, heart-shaped form borne on a 

 short smooth peduncle without axis, and with but two canals. 

 Zooids numerous. 



Genus RENILLA. 



The genus, being the only one, has the character of the family. 



RENILLA AMETHYSTINA Verrill. 



Plate LXXXVII, fig. 11. 

 Renilla amethystma Verrill, Bull. Mus. Comp. Zool., 1864, p. 29. 



Numerous specimens of this beautiful species were found in shallow 

 water in the bay of San Diego, and were kept alive in the laboratory 

 at La Jolla. 



The frond of the living colony has the power of considerable 

 muscular contraction, giving an undulatorj" motion to the edges. 

 Some of the fully expanded polj^'ps were at least half an inch long. 

 After they are once expanded they are quite sluggish, and will with- 

 stand handling without retracting. 



Specimens left over night in small dishes of sea water were alive, 

 and expanded readily upon the application of fresh sea water in the 

 morning. 



Distribution. — Bay of San Diego, shallow water; Panama, Pearl 

 Islands, and the coast of Peru (Verrill) . 



Order GORGONACEA. 



Colonies fixed, with a more or less distinct axis cylinder around 

 which the cortex is disposed. In branched forms the axis extends 

 throughout the ramifications. 



Suborder HOLAXONIA. 



Axis cylinder well developed, and never consisting of fused spicules. 

 It is composed of a horny substance more or less calcified, or of 

 alternating horny and homogeneous calcareous matter. 



Family PRIMNOID^. 



Polyps with well-developed cal3'^ces, retractile tentacles, and an 

 8-parted operculum composed of modified spicules attached to the 

 calyx. Root calcareous. 



Genus CALIGORGIA. 



Calyces club-shaped, calyx scales ctenate with radiating ribs. 

 Calyces regularly in whorls of more than three. 



