344 P. M. DUNCAN ON SOME FOSSIL REEF-BUILDING COEALS 



and their upper edge, finely dentate, dips down very slightly towards 

 the columella. Some septa are continued on to long and wavy 

 costae, which become thickened halfway between the calices ; and 

 others soon unite to two or even more costae, or simply bifurcate in 

 their path towards the nearest corallites. Occasionally there are 

 three costae united to one septum. The costae are long, slightly 

 wavy, slightly exsert, narrow, except midway, and are dentate at 

 their free edge. The small spiny dentations, when removed, leave open 

 pits on the surface of the costae, which give them a very characteristic 

 appearance. The costae are also finely and distinctly granular late- 

 rally ; but the tips of the grains do not meet. There are eighty costae 

 in connexion with the calicular septa in the largest corallite. 



The sides of the septa are marked with closely packed, large, but 

 flat granules, as are those of the costae (as seen in sections) ; and the 

 endotheca is largely developed, being close, and curved both upwards 

 and downwards. It reaches to the columellary space, across it, and 

 high up in it. 



The wall appears to be rudimentary; and the costae are united by 

 exotheca and by a growth from their sides. Synapticulae barely 

 exist ; for it is very rare to find a few of the lateral granules of the 

 costae and septa attached by their ends. 



Diameter of largest calice T 6 jj inch. 



Alliances. This is a well-marked species, and has large calices, 

 long dentate costae, and largely developed endotheca and exotheca, 

 the synapticular element being very small. It is the only form of 

 the genus which has hitherto been discovered in deposits later in 

 age than the Nummulitic ; and it does not closely resemble those 

 from that series*. Very Jurassic in its appearance, the coral would 

 almost pass for Thamnastrcea Walcotti, nobis f, from the Inferior 

 Oolite of England ; and it has no alliance, except that of a generic 

 nature, with the species from the Indian Cretaceous rocks. 



Thamnaste^a, species. 



A much-worn specimen of a Thamnastraean, greatly resenbling 

 and probably identical with the last-described species, was cut, and 

 microscopical sections were made. One section passed through 

 several corallites at a slight distance from the surface ; and another 

 was taken in a longitudinal direction and parallel with the septa. 

 A wall separating the corallites is not to be found, and the costae 

 are continuous with the septa of different calices, the laminae being 

 bound together by their sides. The septa and dissepiments, es- 

 pecially the former, are marked by opaque and either rounded or 

 more or less elongate spots, which apparently coincide with the 

 large granules which constitute the beauty of the ornamentation of 

 the septa. These granules are very numerous and evidently are 

 of more importance than simple ornaments ; for the microscope 

 shows them to be centres of sclerenchymatous spicular growth. 

 They are probably ill-developed synapticulae. 



* Consult D'Achiardi, Coralli Eocenici del Friuli, 1875. 

 t Pal. Soc. Supplement to Brit. Foss. Corals, Oolitic part. 



