CORALS FROM THE INFERIOR OOLITE. 139 
3. Isastrea LoNnspDALII. 
All the specimens of this species which we have seen were in so bad a state of preser- 
vation, that we did not consider them worthy of being figured in this Monograph. The 
calices are not very unequal in size, and rather shallow; the septa are thin, straight, and 
form four cycla; those of the first two cycla differ but little in size; the last cyclum is 
more or less incomplete ; great diagonal of the calices two lines and a half. 
This fossil was found in the Inferior Oolite at the foot of Lansdown, near Bath, and 
was given to the Geological Society of London by Mr. Pratt. 
Some casts found in the Inferior Oolite at Charleomb and at Dundry, appear to belong 
to corals of this genus; they show very unequally developed prismatic calices, but cannot 
be characterised specifically. 
Genus THAMNASTREA, (p. xlii.) 
1. ToamnastrEA Drrranciana. ‘Tab. XXIX, figs. 3, 3a, 34; and 4, 4a, 44. 
Astrea Durranciana, Michelin, Icon. Zooph., p. 9, tab. ii, fig. 1, 1840. 
SynastrReA Durrancrana, Milne Edwards and J. Haime, Ann. des Sc. Nat., s. 3, vol. xii, 
p. 153, 1849. 
= — D' Orbigny, Prod. de Paleont., tab. i, p. 292, 1850. 
THAMNASTREA Drrranciana, Milne Edwards and J. Haime, Polyp. des Terr. Palzoz., &., 
p. 110, 1851. 
Corallum in general thin, discoid or somewhat turbinate ; its common basal plate 
covered with a complete epitheca strongly wrinkled ; its upper surface almost flat, in some 
slightly convex, in others concave. Cadices superficial, arranged in concentric lines, rather 
irregular, and having a very small central fossula. Colwmel/a quite rudimentary. Septa 
very closely set, very thin, rather flexuous, and in general more developed in the direction 
of the radii of the compound corallum, than in the opposite direction, completely confluent, 
and presenting very closely set, regular crenulations at their upper edge. In general they 
form three complete cycla; but in some individuals the third cyclum is rather incomplete, 
and in others rudiments of a fourth cyclum appear in some of the systems. Breadth of the 
calices one line and a half. 
- 
When the calices are worn down, the polygonal wad/s become very distinct (fig. 34), 
and this coral then assumes an appearance very similar to that of a fossil, much weather- 
worn, that was found at Dundry by our friend Mr. Bowerbank, and is figured in our 
XXIXth Plate under the number 4; the size of the calices is not quite the same, and we 
