FAM. 4. ALCYONIIDAE.—The colonies of this family are usually soft and fleshy, and the spicules, evenly distributed throughout the coenenchym, do not usually fuse or interlock to form a continuous solid skeleton. They may be unbranched or lobed, never dendritic in form. The principal genera are:—_Alcyonium_, Linnaeus, cosmopolitan, but principally distributed in temperate and cold waters. _Alcyonium digitatum_ is the commonest British Alcyonarian. It is found in shallow water, from the pools left at low spring tides to depths of 40 or 50 fathoms, at most places on the British shores. It is stated by Koehler to descend into depths of over 300 fathoms in the Bay of Biscay. There are two principal varieties; one is white or pale pink in the living condition, and the other yellow. In some localities the two varieties may be found in the same pools. Another species, _Alcyonium glomeratum_, placed in a distinct genus (_Rhodophyton_) by Gray, and distinguished from the common species by its red colour and long digitate lobes, is found only off the coast of Cornwall. _Paralcyonium_, Milne Edwards; Mediterranean. _Sclerophytum_, Pratt; sometimes dimorphic, Indian Ocean. _Sarcophytum_, Lesson; dimorphic, principally tropical. _Lolophytum_, Marenzeller; dimorphic, tropical. _Anthomastus_, Verrill; dimorphic, Atlantic Ocean, deep water. _Acrophytum_, Hickson; dimorphic, Cape of Good Hope. FAM. 5. NEPHTHYIDAE.—Colonies dendritic. Usually soft and flexible in consistency. _Nephthya_, Savigny; Indian and Pacific Oceans. _Spongodes_, Lesson; widely distributed in the Indian and Pacific Oceans. FAM. 6. SIPHONOGORGIIDAE.—Colonies often of considerable size. Dendritic. Spicules usually large and abundant, giving a stiff, brittle consistency to the stem and branches. _Siphonogorgia_, Kölliker; Red Sea, Indian, and Pacific tropics. _Chironephthya_, Wright and Studer; Indian and Pacific Oceans. _Lemnalia_, {350}Gray; Zanzibar. _Agaricoides_, Simpson;[375] Indian Ocean, 400 fathoms. ORDER IV. GORGONACEA. This order contains a very large number of dendritic and usually flexible corals occurring in nearly all seas and extending from shallow waters to the very great depths of the ocean. A large proportion of them are brightly coloured, and as the principal pigments are fixed in the spicules, and are therefore preserved when the corals are dead and dried, they afford some of the most attractive and graceful objects of a natural history museum. The only character that separates them from the Alcyonacea is that they possess a skeletal axis that is not perforated by the coelenteric cavities of the zooids. The coelenteric cavities are usually short. The order may conveniently be divided into two sub-orders. SUB-ORDER 1. PSEUDAXONIA.