434 ZOOPHYTES. 



nate. All the cespitose species, however, are not subject to this vari- 

 ation. 



Among the species of Madrepora, there are some in which one of 

 the tentacles of the polyps is long and flexible. This was observed 

 in a cespitose species (M. prostrata) having thin labellate calicles. 

 But whether it belongs or not to all the horizontally growing species 

 with similar calicles, remains to be determined. This character may 

 hereafter lead to a subdivision of the genus, and a separation of the 

 species having labellate calicles, (M. conigera, efflorescens, cytherea, 

 spicifera, hyacinthus, surculosa, millepora, prostrata, subulata, tur- 

 binata, and convexa,) as a distinct group. 



Madrepores are among the most important of reef-forming corals, 

 and grow in great profusion about the outer reefs, as well as within 

 the bays, channels, and lagoons, enclosed by coral barriers. Some 

 species attain a large size, though compared with the forest trees of 

 the land, trees of coral growth dwindle to mere nursery saplings. 

 The staghorn Madrepore (M. cervicornis) is sometimes six to eight 

 feet in height, and the vase corals spread to a diameter of four or fi-ve 

 feet. Huge plates of a foliate Madrepore are often thrown on the 

 shores of some of the Pacific islands, measuring six feet square and 

 three to six inches in thickness, which are but portions of a zoophyte, 

 probably three or four times as large. The species called Neptune's 

 Chair (M. palmata), from the West Indies, grows in stout, deeply 

 divided plates, spreading from a common footstalk or pedicel ; and 

 occasionally the whole coral plant is six or seven feet high and nearly 

 as many broad, with the pedicel six or eight inches through. 



The genus Madrepora* of early authors included all coral zoophytes 

 with stellate cells, and thus embraced the Astrsea and Caryophyllia 

 tribes, along with the Madreporacea. It was restricted by Lamarck 

 to the limits here adopted. 



The Seriatopora, Sideropora, and Pocilloporse, differ from the 

 Madreporae, not only in the closed bottom of the cell, and the trans- 

 verse septa within, but also in the absence of all calicles, the nearest 

 approach to which is found in a slight vaulting above, or a promi- 

 nence of the upper side of the cell. 



* Madrepora is an Italian word, from the Latin mater, motJier, and poms, pore, used 

 for a porous stone: because it produces stone? See a note by Ehrenberg, op. cit. Berlin. 

 Trans., 1832, p. 345. 



