XIII ALCYONARIA GORGONACEA 355 



Fam. 3. Chrysogorgiidae.^ — The axis in tliis family is com- 

 posed of a ]iorny iibrous substance witli interstratified calcareous 

 jiarticles, and it springs from a calcareous plate, which sometimes 

 gives off root-like processes. It may be unbranched or branched 

 in such a way that the branches of the second, third, and subsc- 

 (|uent orders assume in turn the direction of the base of the 

 main axis. The axis is frequently of a metallic iridescent 

 appearance. The zooids usually arise in a single straight or 

 spiral row on the branches, and are not retractile. The 

 coenenchym is thin. The spicules vary considerably, Ijut in a 

 very large proportion of the species they are thin, oval, or hour- 

 glass plates (Fig. 149, 10, p. 336). 



By some authors this family is considered to be the simplest 

 and most primitive of the Axifera ; but the delicate character of 

 the axis of the main stem and branches, the thinness of the 

 coenenchym, the position of the zooids on one side of the branches 

 only, and the tenuity of the calcareous spicules may be all 

 accounted not as primitive characters, but as special adaptations 

 to the life in the slow uniform currents of deep water. 



The principal genera are : — Lepidogorgia, Verrill ; Atlantic 

 and Pacific Oceans, 300 to 1600 fathoms. Axis unbranched. 

 Zooids large and arranged in a single row. Trichogorgia, 

 Hickson ; Cape of Good Hope, 56 fathoms. Colony branching 

 in one plane. Zooids numerous and on all sides of the branches. 

 Chrysogorgia, D. and M. ; deep water. Axis branched. Spicules 

 on the zooids always large. Metallogorgia, Versluys ; Atlantic 

 Ocean, 400 to 900 fathoms. Basal part of the stem imbranched 

 (mouopodial). Iridogorgia, Yerrill. vSpiral stem and Ijranches. 

 PIcurogorgia, Versluys. Axis branched in one plane. Coenen- 

 chym thick. Riisea, D. and M. Monopodial stem and thick 

 coenencliym. 



Fam. 4. Muriceidae. — Tliis is a large family, exhibiting very 

 great variety of haldt. The spicules are often very spiny, ami 

 project beyond the surface of the ectoderm, giving the colony a 

 rough appearance. A great number of genera have been described, 

 l)ut none of them are very well known. The family requires 

 careful revision. 



The more important genera are: — Acanthogorgia, Gray; 

 principally in deep water in the Atlantic Ocean. The calices arc 



^ For a revision of tliis family, see Versluys, Siborja Expcditic, xii. 1902. 



