INTRODUCTION. xli 



64. Genus Astroides. 



Quoy and Gaimard, Ann. des Sc. Nat., l re serie, vol. x, p. 187, 1827 ; Astrqitis, Dana, Zooph., p. 405, 1846. 



Corallum incrusting, and formed of corallites very unequally approximated; some 

 almost entirely free, others crowded so as to become polygonal, but always separated by a 

 more or less developed epitheca. Gemmation extra-calicular. Calices deep. Columella 

 spongy, large, and projecting very much at the bottom of the fossula, a character which 

 does not exist in any of the preceding Astreinse. Septa not much developed, very thin, 

 not exsert, irregularly and delicately denticulated. Dissepiments very abundant. Walls 

 composed of a dense spongy tissue. Epitheca complete. 



Typ. sp., Astroides calicularis, Blainville, Diet, des Sc. Nat., vol. Ix. ; Caryophyllia calicularis, Lamarck, 

 op. cit., vol. ii, p. 226 ; Milne Edwards, Atlas du Regne Anim. de Cuvier, Zooph., tab. lxxxiii, fig. 2. 



65. Genus Prionastrea. 



Milne Edw. and J. Haime, Comptes rend., t. xxvii, p. 495, 1848. 



Corallum forming a convex or gibbose mass, the under surface of which constitutes a 

 common plate, covered with a thin, complete epitheca. Gemmation sub-marginal. Calices 

 distinct, polygonal ; fossula deep ; margins united so as to form a simple crest between 

 the different corallites. Columella spongy. Septa thin, crowded, delicately granulated on 

 their sides, and strongly dentated at their apex ; the largest of these teeth are those nearest 

 the columella. Dissepiments well developed. Walls in general independent towards the 

 basis of the coral, but uniting to the adjacent ones near the calices, so that the visceral 

 chambers appear to be separated only by a single simple lamina. 



Typ. sp., Prionastrea abdita, Milne Edw. and J. Haime, loc. cit. ; Astrcea abdita, Lamarck, Hist, des 

 Anim. sans Vert., t. ii, p. 265, 1816 ; Madrepora abdita, Soland. and Ellis, t. 50, f. 2. 



66. Genus Siderastrea. 



(In parte) Blainville, Diet, des Sc. Nat., t. Ix, p. 335, 1830 ; Siderina, Dana, Zooph., p. 218, 1846. 



Corallum incrusting, forming a convex mass of a very dense tissue. Gemmation 

 sub-marginal. Corallites united by their walls, which are thin, and sometimes indistinct. 

 Calices sub-pentagonal, with a deep fossula, and their margins rendered thick by the pro- 

 longation of the septa. Columella papillose, in general not much developed, but having a 

 tendency to become compact. Septa very closely set, thin, and regularly denticulated ; 

 their lateral surfaces covered with large granulations, which come in contact with those of 

 the adjoining septa, but are not united to them. Dissepiments rudimentary. 



Typ. sp., Siderastrea galaxea, Blainville, loc. cit. ; Madrepora galaxea. Ellis and Solander, Hist, of 

 Zooph., tab. xlvii, fig. 7. 



67. Genus Baryastrea. 



Milne Edw. and J. Haime, Comptes rend, de l'Acad. des Sc, t. xxvii, p. 495, 1848. 



Corallum incrusting ; its tissue very dense and compact. Gemmation marginal or 

 sub-marginal. Corallites very intimately united by their walls. Calices polygonal and 



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