CORALS FROM THE MOUNTAIN LIMESTONE. 193 



2. Lithostrotion ensifer. Tab. XXXVIII, figs. 2, 2a. 



Lithostrotion ensifer, Milne Edwards and Jules Haime, Pol. Foss. des Terr. Palseoz., 



p. 442, 1851. 



Corattum massive, with a flat or sub-convex surface. Corallites separated only by a 

 very thin epithecal wall, which in some places is scarcely visible. Calices polygonal, often 

 ill-circumscribed, almost flat towards their circumference, and presenting, in their centre, 

 a shallow fossula. Columella stout, compressed, and very prominent. Principal septa 

 about 30 in number, thin, nearly straight, somewhat unequal alternately ; some rudimentary 

 ones. Diameter of the corallites 4 or 5 lines. 



From Clifton, (Bristol Museum.) In this fossil the columella is more prominent than 

 in any other species of the same genus, and the walls much thinner ; by the mode of 

 coalescence of the corallites it bears some resemblance to the genus Phillipsastrcea, in 

 which the walls disappear completely. 



3. Lithostrotion aranea. Tab. XXXIX, figs. 1, la. 



Astrea hexagon a, var. minor? Portlock, Rep. on Londonderry, p. 332, pi. xxiii, fig. 2, 



1843. 

 Astrea aranea, M'Coy, Syn. Carb. Foss. of Irel., p. 187, 1844. 

 Nemaphyllum aranea, M'Coy, Ann. and Mag. of Nat. Hist., 2d series, vol. iii, p. 135, 



1849. 

 Lasmocyathus aranea, D' Orbigny, Prod, de Palseont., vol. i, p. 160, 1850. 

 Lithostrotion aranea, Milne Edwards and Jules Haime, Pol. Foss. des Terr. Palseoz., 



p. 443, 1851. 



Corallum massive. Corallites irregularly polygonal, some of their sides being some- 

 times curved, whilst most of them are straight. Inner wall rather distinct. Columella 

 compressed ; its transverse section fusiform. Septal radii very thin, but well developed, 

 and slightly flexuous ; 22 or 24 principal ones, extending almost to the columella ; an 

 equal number of smaller ones that do not reach to the inner wall. Great diameter of the 

 Calices about 6 lines ; that of the inner wall about half. Dissepiments of the exterior 

 zone very numerous, and forming small, closely set vesicles. Tabula appearing to be 

 numerous, and much raised towards the centre by the Columella. 



Found at Armagh, Ireland ; the specimen represented in this Monograph belongs to 

 the collection of M. de Verneuil. 



The fossil which Col. Portlock considers as a small variety of the Astrea hexagona 

 belongs probably to this species j it was found in Ireland. 



