part 2] RUGOSE CORALS FROM THE BURINDI SERIES. 163 



Tabulae. — The tabulse are represented by small, strongly- 

 arched plates — the tabelke 1 (PL VIII, fig. 2). The area occupied 

 by the tabular tissue is a comparatively narrow one. the intrathecal 

 region being largely taken up by the columella. 



Dissepiments. — The dissepiments are very small and very 

 strongly arched, and in the adult stage build up a wide extrathecal 

 region constituting as much as three-quarters of the radius of the 

 corallum. 



Epitheca. — This wall is thin, and is therefore readily destroyed 

 hj erosion or exposure. 



Ontogeny. 



Unfortunately, in none of the collected specimens are the initial 

 stages of the corallum preserved. The ' proximal end ' is missing 

 in every case. The earliest section examined (which was approxi- 

 mately 12 - 5 mm.) represented quite a late neanic stage: at this 

 stage the columella has attained its characteristic form and pro- 

 portion ; but the dissepimental tissue is undeveloped, and the septa 

 are united to a stout epitheca. While the major septa (about 30 

 in number) reach the columella, the minor are merely rudimentary, 

 not being more than 1 mm. in length. The coral at this stage 

 somewhat resembles Cyathaxonia. 



As the corallum develops, the septa become reduced at the 

 then ' outer ends ' (where they join the epitheca) to a mere lamella, 

 and may finally become entirely separated from this outer wall. 



Affinity and Comparisons. 



Amygdalopliyllum etlieridgei is very similar to ' Oyathophyl- 

 lum ' (JPaloBosmilia) murchisoni Edwards & Haime in all its 

 structural details, except in the development of a columella, and 

 there can be little doubt that the former species is a modification 

 of the latter. The numerous slender septa, 3 the extensive develop- 

 ment of dissepimental tissue forming a wide extrathecal region, 

 and the tendency towards the separation of the septa and epitheca 

 are the same in the two genera. In both cases, moreover, the 

 major septa meet at the centre of the corallum, and their inner 

 ends are more or less twisted ; but, while in Palceosmilia mur- 

 chisoni the inner ends ©f the septa are free, in Amygdalophyllum 

 etheridgei these are embedded in a true columella. Sections of 

 Palceosmilia murchisoni and Amygdalophyllum etheridgei are 

 (for comparison) shown close to each other in PI. IX, figs. 1 & 2. 



It may be mentioned here that the columella of liugose Corals 

 originate as a dilation of the middle region of the axial septum, 



1 S. Smith, Q. J. G-.S. vol. Ixxi (1915-16) p. 225. 



2 In corals in which there are comparatively few septa, the septa and 

 epitheca arc relatively thick ; in forms having numerous septa, the septa and 

 epitheca are thin. 



