TRIBE I. ASTR^ACEA. 155 



cells may be simple, belonging to a single polyp, or a long line or 

 series may be united, so as to form a meandering trench. There are 

 thus the simple and meandrine forms of the calicularly branched 

 species, as well as of the aggregate. Like the latter, these segregate 

 zoophytes are usually hemispherical, remarkably perfect in sym- 

 metry, and often many feet in diameter. 



Besides these, there are also foliated species. The folia are some- 

 times clustered in convex clumps (Merulinae), and each leaf is grace- 

 fully and delicately modelled, the ridges of the surface constituting 

 its nervures. The cells are indistinct, and lie in furrows between the 

 ridges, and the species, therefore, are properly foliaceous Meandrinse ; 

 the lamellae of the ridges are a little oblique, owing to the mode of 

 grow th. Branching forms also occur of the same general character. 



A few of the foliaceous Astrseidse (Echinoporse) have the surface 

 simply striated and spinulous, and the cells are circular and some- 

 what prominent ( 76). A branching species of this genus is a con- 

 necting link between these corals and the Oculinse. 



Other foliate species (Tridacophyllise) have large expanded cells, 

 partially enclosed by ascending folia, which are striated with narrow 

 and nearly entire lamellae. The folia correspond to the septa of other 

 species, which are here thin and leaf-like. Other cells often occur on 

 the surfaces of the folia, in which case, they resemble the Pavonise. 



Besides the instance of the branching Echinopora uniting this 

 family to the Caryophyllidse, through the Oculinae, there are also cer- 

 tain tubular AstrseaB, which approximate in their coralla closely to 

 other CaryophyllidaB, and especially to the genus Astreopora and 

 Astroitis, in which, as the species are massive, the mode of budding 

 cannot always be easily determined. The many transverse dissepi- 

 ments, uniting the lamellse by their lateral surfaces, will seldom fail, 

 however, to distinguish the Astrseas. The characters separating them 

 from the Cyathophyllidoe, will be stated in the remarks upon that 

 family. 



The corals of this family are confined, with rare exceptions, to the 

 coral-reef seas. 



The annexed table gives a view of the genera of Astraeidae, as used 

 by different authors since Lamarck. 



