618 THE WONDERS OF GEOLOGY. Lect. VI. 



restricted to tropical climates. Several species of this 

 genus occur in a fossil state ; a very beautiful species is 

 often met with in the Maestricht limestone (ante, p. 320, 



fig- 5). 



18. The red coral ; Corallium rubrum. — I advance 

 to the examination of the polyparia having an axis com- 

 posed of a calcareous stony substance ; and one genus of 

 which possesses a skeleton of so beautiful a colour, and 

 susceptible of so fine a polish, as to be largely employed for 

 ornamental purposes. The Red Coral is a branched zoo- 

 phyte, somewhat resembling in miniature a tree deprived of 

 its leaves and twigs. It seldom exceeds one foot in height, 

 and is attached to the rocks by a broad expansion or base. 

 It consists of a brilliant red stony axis, invested with a 

 fleshy or gelatinous substance of a pale blue colour, stud- 

 ded over with stellular polypes. This figure (PL V.^. 

 9), represents a branch of Coral with several polypes, 

 highly magnified, as seen alive in the water. The cortical 

 or fleshy substance is removed at the extremities of the 

 branch, and the red stony axis exposed. As the cells of 

 the polypes are only composed of the soft animal matter 

 which rapidly undergoes decomposition after death, no 

 traces of their structure remain on the durable skeleton. 



The Red Coral, as is well known, is of a very hard 

 and durable texture ; it is obtained by dredging in 

 different parts of the Mediterranean and Eastern seas, 

 and forms an important article of commerce. It varies 

 much in hue, according to its situation in the sea : in 

 shallow water it is of the most beautiful colour, a free 

 admission of light appearing necessary for its full develop- 

 ment. It is of slow growth ; eight or ten years, in a 

 moderate depth of water, being necessary for it to reach 

 maturity. Arrived at this period, it extends but very 

 slowly, and is soon pierced on all sides by those destructive 

 animals which attack even the hardest rocks ; it loses its 



