96 



PROP. P. MARTIN DrNCAN's REVISION OF THE 



series, witli their walls fused throughout, so as to form a simple, 

 very thin line of separation between the series. Calicinal centres 

 generally distinct, indicated by the curving of the septa. Costse 

 almost entirely absent. Epitheca very slightly developed. Septa 

 thin, fragile, very prominent, distant, edge entire. Columella 

 absent. Endotheca well developed, vesicular ; the dissepiments 

 continuous between the septa from the centre of the calicle to the 

 wall, very convex above, rather far apart above each other, thus 

 forming wide interseptal chambers. Owing to this great develop- 

 ment of vesicular ecdotheca, the series of calicinal centres are 

 separated by wide ridges formed entirely by the thin wall and by 

 the convex dissepiments which stretch from the centre to this 

 thin wall. 



Distribution. — 'Recent. Banda. 



Genus Phytogtra, d' Orbigny^Note sur les Polyp, foss. p. 6(1849) ; 

 Cours JElement. de Fal. t. ii. p. 163, fig. SOI (1852). 



Colony formed of rather thick, low, horizontal branches, free at 

 the sides and below, composed of series of short corallites, whose 

 calicinal centres are indistinct, and whose wall is naked and costu- 

 late. The columella is lamellar and continuous. The septa are 

 entire and unequal, large. Increase by fissiparity. 



Distribution. — Fossil. Jurassic : Europe. 



D'Orbigny considers this genus to be a JPlerogyra from its large 

 alternate septa, but it has a lamellar columella. The figure given 

 by him shows a trifurcate branch. 



IV. Alliance MONTICULOIDA. 

 Astraeidse with fissiparous and serial coralhtes, united by their walls, 

 which form prominent collines radiating more or less, or monticules 

 marked by costse. 



Genus Aspidiscus, Koenig. 

 Genus Hydnophora, Ed. & H. 

 Genus Monticulastr^a, Duncan. 



Genus Aspidisctis, Koenig, 1825 ; Milne-Edwards Sf Jules Haime^ 

 Sist. Nat. des Corall. vol. ii. p. 386 (1857), amended. 

 Colony subhemispherical, free. Under surface concave, and 

 marked by a well-developed concentrically folded epitheca. Series 

 of corallites radiating from a short, straight, polar colline to above 

 the margin of the base ; some series long, others between them 



