CORALS FROM THE GREAT OOLITE. 117 



is in part established by the species which, like /. serialis and /. Lotharinga, form some- 

 times a short series of calices where gemmation is very active, and by those Latomeandra 

 which are of a massive form. But in all well-preserved fossils belonging to the latter 

 genus we have found the common basal plate naked, and presenting simple straight costse, 

 whereas in Isastrea the basal plate is covered with a complete epitheca, and when that 

 tunic is worn away the costal striae assume the appearance of radiate fossulse. M. 

 D'Orbigny has recently formed the genus Meandrophi/llia} for the species which are in 

 some respects intermediate between these two types, having the calices elongated and often 

 arranged in short series ; but it appears useless to separate generically all the degrees by 

 which one form passes to another, and when the principal characters peculiar to one or the 

 other of the above-mentioned types become obscure, as in the present case, we prefer 

 having recourse to the secondary characters just pointed out, in order to determine the 

 genus to which the doubtful species is to be referred. 



• 



Genus Clausastrea." 



Clausastrea Pratti, Tab. XXII, fig. 5. 



CoralJuM massive, terminated by a slightly convex surface. Calices large, some- 

 what unequal, and not separated by a distinct wall. Columella spongiose, well developed. 

 Septa of the adjoining corallites quite confluent ; some of them enlarged or much bent at 

 their point of junction with the corresponding ones from another individual. They are 

 about thirty in each calice ; they are rather thin, unequal in size, closely set, and present 

 vertical striae on their lateral surfaces : the smaller ones are united to the neighbouring 

 large ones by their inner edge. The loculi are closed by well-formed and rather numerous 

 dissepiments. The common basal plate is covered with thick granulated costal striae, and 

 does not appear to have any epitheca. Diameter of the calices five or six lines. 



We have as yet seen but one ill-preserved specimen of this species ; it was found at 

 Comb-Down, near Bath, and belongs to the collection of the Geological Society. It has not 

 enabled us to give a complete description of this species, but may easily be distinguished 

 from the other two species which remain in the genus Clausastrea as now circumscribed, 

 that is to say characterised, by the absence of walls and columella.^ In C. Pratti the 

 septa are much thicker than in C. tessellata^ and in C. consohrinaJ' 



1 D'Orbigny, Note Sur des Pol. Foss., p. 8. 



2 D'Orbigny, Note Sur des Pol. Fossiles, p. 9, 1849. 



^ See the Introduction to our Memoir on the Palseoz. Fossil Corals, etc., in the ' Arcliives du Museum,' 

 vol. V, p. 10". 



* D'Orbigny, Prod., vol. i, p. 293. 



^ Synastrea consubvina, D'Orbigny, loc. cit. Chnisastreal consohrina, Milne Edwards and Haime, 

 loc. cit. 



