FAMILIES AND &ENEEA OE THE MADBEPOEAEIA. 



109 



and slightly undulating (entire ?). There are 36 septa, unequal 

 accordiog to cycles. 



Distribution. — Fossil. Cretaceous : Europe. 



G-enus Pleijeosttlina, FJ. de Fromentel, Introd. a Vetude des 

 Polyp, foss, p. 201 (1858-61). 



Colony in a convex mass or in extended laminae. Calices 

 circular or polygonal in places. Septa entire, few ; one large 

 septum reaches the centre of the calice and swells there, after the 

 fashion of a columella. Corallites united by their walls or by 

 epitheca, which covers the walls. Common plateau naked and 

 costulate, or presenting a slightly developed epitheca. 



Distribution. — Fossil. Oolite : Europe. 



There is much that is unsatisfactory about this genus. The 

 epitheca uniting the corallites and not covering the " plateau 

 commun " is difficult to understand. Perhaps the author of the 

 genus meant exotheca uniting the corallites. 



III. Alliance STYLINOIDA. 



Massive budding Astraeidse, with corallites united by their costse or by 

 exotheca. Columella styliform. Septa entire and dentated. Pali may 

 be present or not. 



Tribe I. With entire septa. 



Genus Stylina, Lmk. 



Genus Psammoccenia, Ed. & H. 



Tribe II. With dentate septa. 



Genus Columnastr^a, Ed. & H. 



Genus Stylastr^a, E. de From. 

 Helioccenia, Etallon, appears to be a subgenus of Stylina. 



Tribe I. 



Genus Sttl^a, Lamarck, 1816; Milne - E dw ar ds Sf Jules Haime, 

 Hist. Nat. des Corall. vol. ii. p. 233, amended. 



Colony in the form of subplane, convex, gibbous masses, or 

 dendroid. The corallites are united by their costse and well- 

 developed exotheca, or only here and there, and terminate at the 

 free surface in little conical elevations more or less projecting. 

 The calices on these elevations are for the most part circular, 

 free at their margins, and usually distant. The columella is 

 styliform and projects. The septa are exsert, well developed, 



