298 



NATURAL HISTORY. 



have a spiny outside. This genus is the type of a sub-family* in which there is a row of pali, 

 and it is found that the interseptal spaces, when the soft parts are washed away, are open throughout. 

 One genust increases by budding, and is therefore compound. 



A sub-family which is but slightly represented now, and which had a great development in 

 the Secondary and Tertiary ages, is that of the Trochocyathaceae, and it has more than one row 

 of pali, and consequently as many extra rows of tentacles. Sevei'al of its genera are now repre- 

 sented in the deep sea, and Deltocyathus is the most widely distributed, being found, moreover, 

 at the depth of 2,250 fathoms. 



Another sub-family is that of the Turbinolinse, and it is characterised by the simplicity of 

 the hard parts, there being the cup or wall, septa, and costae. Sometimes the columella exists, 

 and an epitheca, but pali are not seen. Some of these simple forms are extinct, and the majority 

 still live. They are divided into genera by the shape of the Coral, which, for instance, is compressed 

 and fan-shaped in Flabellum and wedge-shaped in Sphenotrochus ; and by the nature of the 

 columella, which is styliform in Turbinolia and fascicular in others. Some, such as Blastotrochus, 

 bud on the outside. Many of the species of this sub-family are dwellers on the floor of the deep 

 sea, and the fossil forms are very numerous. The third sub-family is that of the Dasnndae, and 

 the only genus is extinct. 



FAMILY OCULINIDJE. 



These are branching Corals, which bud on the outside of the stem, or on the edge of the 

 calices, and have these last resembling, more or less, those of the family just noticed. There 

 are, however, dissepiments in the interseptal spaces of some, and in the common Lophohelia prolifera, 

 found on the floor of the North Atlantic, horizontal layers of hard tissue may cross the whole internal 

 cavity, and are called tabulae. Moreover, the lower parts of the cup fill up with carbonate of lime, 

 and there is a general solidity of the branches. The genera are numerous, and many are extinct, 

 whilst others inhabit great depths. A small sub-family, the Stylophorinsa, increase by the process of 

 budding, or gemmation, but the hard tissue is not so compact as that of the others, and the 

 columella is styliform. 



FAMILY ASTILEID^E. 



This family consists of a vast number of genera, many of which are reef-builders; others 

 are simple forms, and several are extinct. The hard parts have all the structures hitherto mentioned, 



and there are septa, costae, a columella, 

 endothecal dissepiments, epitheca, and 

 buds. There is also exotheca in the 

 compound forms. They are divided arti- 

 ficially into two groups : those with the 

 tops of the septa plain the Eusmilinse 

 and those with serrations, or spines, on 

 the tops of the septa the Astraeime. 

 The first sub-family of the Eusmilinaa is 

 a very ancient one, the Trochosmiliaceae, 

 and they are solitary Corals, cup-shaped, 

 and with the internal dissepiments well 

 developed. 



The sub-family Euphylliaceae grow 

 in bulk by fissiparous division of the 

 calices. These elongate in one direction 

 and divide, and the separate portions become isolated more or less above, but still remain parts of 

 the original Coral. Some form tuft-shaped Corals, free, to a great extent, at the surface, and 

 others are only isolated at the calicular surface, and form masses, and a third group are completely 

 fixed and confluent, forming very diverse-shaped Corals. 



Anothei- sub-family is that of the Stylinacese, which was largely represented in the Mesozoic and 



FAVIA PALLIDA. 



CaryopkyUiacci: 



t Ccenocyathus. 



