MADREPORARIAN CORALS 91 



filled with forests of the branches of specimens which are 

 rooted on the rocks of the sea-bottom.^ 



The specimens the naturalist finds exposed at low spring 

 tide do not as a rule attain to the same gigantic proportions 

 as the massive Porites, but the branching specimens in 

 deeper water outside the reef must be often many feet in 

 height, with main stems nearly a foot in diameter. Massive 

 colonies twenty to thirty feet in length are also found in 

 some localities.- 



The genus is found both in the West Indies and in the 

 Indo-Pacific Ocean, the limits of its geographical distribution 

 being almost identical with that of the coral reefs of the 

 world. The forms assumed by the colonies are so varied 

 and so much influenced by the local conditions and surround- 

 ings that it is quite impossible to express in a few words all 

 the possible varieties of shape that a colony of Madrepora 

 may assume. There are, however, three types of construc- 

 tion which may be recognised in a large collection of these 

 corals, known respectively as Forma paUnata, Fonna pro- 

 lifera, and Forma cervicornis. 



In Forma palmata the colony arises from a short, thick 

 stem attached to its support by a spreading or encrusting 

 base, and divides rapidly into a number of branches which 

 ramify and anastomose to form a fan-shaped or leaf-like 

 frond, erect, oblique, or at right angles to the stem from 

 which it arises. 



In Forma prolifera the branches arising from a short 

 stem divide and ramify to form an irregular bush-like 

 growth, with usually less anastomosing of the branches than 

 in Forma palmata. 



In Forma cervicornis there is usually a long, thick, erect 

 main stem, from which large, irregular, lateral branches are 

 given off, which subdivide and but rarely anastomose. This 

 form has the popular name Stag's-horn coral. 



There are many intermediate forms between these three 

 types and others that are massive, lobate, encrusting or 

 lamelliform, and seem to be quite distinct. 



^ See photographs in Saville-Kent's Great Barrier Reef of Australia. 

 ^ Reference may be made to the large specimens in the British Museum. 



