114 BRITISH FOSSIL CORALS. 
We have seen but one specimen of this species ; it was very ill preserved, and had been 
found at Comb-Down, near Bath, by Mr. Pratt. 
This fossil, as far as we are able to judge of its characters, appears to differ from all 
other Isastrea by the tetragonal form of its calices and the small number of septa, relatively 
to the size of the corallites. 
2. Isastrea timiTatTa. Tab. XXIII, figs. 2, 2a, and Tab. XXIV, figs. 4, 4a, 5. 
AstroitEs, ete., R. Plot, Nat. Hist. of Oxfordshire, p. 88, tab. xi, fig. 6, 1676 (good figure: 
i 
we are inclined to think, that fig. 7 represents a specimen in which 
the ceutre of the calices had been accidentally filled up, so as to produce 
the appearance of a styliform columella). 
Manprevora, J. Walcott, Description and Figure of Petref., found near Bath, p. 47, fig. 63, 
WHE 
AsTREA Limirata, Lamouroux, in Michelin’s Iconogr. Zooph., p. 229, tab. xciv, fig. 10, 
1849. 
— — M‘Coy, Ann. and Mag. of Nat. Hist., s. 2, vol. 2, p. 418, 1848. 
PRIoNaSTREA LimiTaTa, Milne Edwards and J. Haime, Ann. des Sc. Nat., s. 3, vol. xii, 
p. 137, 1849. 
PRIONASTREA LIMITATA, P. aLtMENA, and P. Luctnnsis, D’Orbigny, Prod. de Paleeont., t. i, 
p- 322, 1850. 
IsasTREA LIMITATA, Milne Edwards and J. Haime, Polyp. Palzoz., ete., p. 103, 1851. 
Corallum massive, terminated by a flat or somewhat gibbose surface. Cadices almost 
equal in some parts, very unequal in others; the small ones usually situated in the depressions, 
and the larger ones on the gibbose parts of the upper surface. The calices are polygonal, 
not very deep, and terminated by a thin, straight, mural edge. The small ones contain 
scarcely twenty septa, but in the larger ones the number of these laminee amounts to about 
thirty, so that there appears to be in that case three complete cycla, and an incomplete 
fourth cyclum, but the whole of the septal apparatus presents very great irregularity ; thus 
we have often seen between two principal septa two smaller ones, one of which, more 
developed than the other, belonged probably to the second cyclum, and the other must have 
belonged to the third cyclum, but had no corresponding one in the other half of the system 
so composed, All the sevfa are thin, straight, or only slightly curved, and sparingly 
granulated, but presenting well characterised radiate strice on their lateral surfaces. They 
are but slightly exsert, and, far from passing from one visceral chamber to another, they in 
general alternate exteriorly with those of the adjoining corallite. The great diagonal of 
the large calices is about two and a half lines; and their depth one line ; the small calices 
are little more than one line broad. 
This fossil was found by Mr. Pratt in the Great Oolite near Bath. Walcott mentioned 
it having been met with at Hampton Downs. It exists also in the corresponding deposits 
near Caen, at Langrune, Luc, and Ranville. 
