272 



HARD WICKE'S SCIENCE- G OSSIP. 



was split up into three divisions, called Tabulata, 

 Rugosa, and Aporosa. It was thought that the two 

 former were Palaeozoic types of corals, and the third 

 of Neozoic and Recent corals. Let us examine the 



many stories. They are compound corals, whose 

 shapes are modified by the manner in which they 

 grew, so that some are polygonal, or many-sided, 

 and others oval or round. The most remarkable of 



fundamental difference of these three groups. The 1 these tabulate fossil corals are Heliolites, Favosites, 



Fig. 197. — Favosites Gothlatidica. 



A Silurian and Devonian Coral (complete specimen) 

 the polygonal tubes. 



b, young specimen ; c, section showing 



Fig. 198. — Favosites Gothland ica, e~ cluster of tubes of Favo- 

 sites ; d, tubes (magnified), showing tabulae and perforations 

 connecting the tubes. 



Fig. 199.— Syringifora ramulosa. Carboniferous limestone 

 , formation. 



tabulate corals are remarkable, and indeed obtain 

 the name which distinguishes them, for the floors 

 which seem to horizontally split^ them up into so 



Fig. 200. — Heliofiora ceerulea. Recent Alcyonarian CoraL 



the pretty "chain-coral" (Halysites), Syringipora, 

 &c. It will be seen from fig. 198, which shows a 

 magnified section of a very abundant Silurian coral 

 {Favosites Gothlandica), that the coral-tubes — as we 

 may call them — are separated into horizontal chambers. 

 The walls are perforated, as they are in some of the 

 Alcyonaria, possibly for transverse canals. It will also 

 be seen that the interiors of the corals are not radiated 

 — that is, have not these vertical plates springing from 

 the walls which are called septa, or if they are present 

 in tabulate corals they are very feebly marked. This 

 general absence of septa is the leading distinction of 

 tabulate corals. Mr. Mosely thinks that most if not all 

 of this group are in reality not Zoantharians, or true 

 corals, but Alcyonarians, of which the common organ- 

 pipe coral ( Tubipora musica) is the best example. Some 



