CORALS FROM THE GREAT OOLITE. 119 



to which latter species it has been referred by Prof. M'Coy. It differs, however, from C. 

 affinis by its septa, which in the latter are much more unequal in height as well as in thick- 

 ness, and form generally three complete cycla. In T. dendroidea the branches are more 

 cylindrical, and vary much less in diameter ; the septa are thicker, strongly denticulated, and 

 do not appear to have any paliform lobules. T. cadomcnsis^ and C. Waltonr are equally 

 of an arborescent form, but in the former the septa are thin, flexuous, and become united 

 by their inner edge ; and in the latter the aspect of the caUce is quite different, on account of 

 the septa being thick towards their external edge, and on the contrary very thin inwards. 



2. Thamnastrea mammosa. Tab. XXIII, figs. 3, 3«. 



Coralliim massive, tall, subpyriforra, terminated by a mammose surface, and composed 

 of superposed layers, which are intimately united, and most distinct near the basis. 

 Calices small, placed at unequal distances, and often disposed in a radiate order towards 

 the summit of the mammillary protuberances. Fossula well characterised, but not deep, 

 and containing a small tubercular columella. Sixteen or eighteen septa, somewhat 

 unequal and rather thin ; some smaller than the rest, are placed irregularly, the others are 

 straight, or bend towards their outer edge, where most of them join the corresponding 

 one from an adjoining corallite. Diameter of the calices, half a line. 



This fossil belongs to the collection of Mr. Stokes, and appears to have been found in 

 the Great Oolite at Sapperton, in Gloucestershire. 



T. mammosa differs from most species of the same genus by the small size of its 

 calices, its strongly gibbose surface, and its mode of growth by superposed layers. It 

 most resembles T. scifa,^ T. tcnuissima,^ and T. concimia^ but its septa are more equally 

 developed than in the latter, and are much less numerous than the first two. 



3. Thamnastrea scita. Tab. XXIII, figs. 4, ^u. 



Coralliim. massive, terminated by an almost flat surface, and composed of thin super- 

 posed layers, the uppermost of which are often incomplete. Calices small, almost equally 

 dispersed, and shallow ; fossula small ; columella rudimentary. Septa delicate, closely 

 set, and differing somewhat in thickness and in breadth alternately ; they are very 

 unequally confluent, and some are straight, whereas others are flexuous or strongly 

 geniculated; their lateral surfaces appear to be delicately granulated. Diameter of the 

 corallites about three quarters of a line. 



1 Astrea cadomensis, Michelin, Iconogr., tab. liv, fig. 4. 



2 Tab. xxix, fig. 4. ^ Tab. xxiii, fig. 4. 



* Sijnastrea tenuissima, Milne Edwards and J. Haime, Ann. Sc. Nat., 3d ser., vol. xii, p. 191. 

 5 Tab. xviii, fig. 3. 



