INTRODUCTION. xhi 
64. Genus AstROIDES. 
Quoy and Gaimard, Ann. des Se. Nat., 1" série, vol. x, p. 187, 1827; Astroitis, 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 im any of the preceding Astreine. 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, Dict. des Sc. Nat., vol. lx. ; Caryophyllia calicularis, Lamarck, 
op. cit., vol. i, p. 226; Milne Edwards, Atlas du Regne Anim. de Cuvier, Zooph., tab. Ixxxiii, fig. 2. 
65. Genus PRIONASTRKA. 
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. Co/wmella 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. Déssepiments 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. ; Astrea abdita, Lamarck, Hist. des 
Anim. sans Vert., t. ii, p. 265, 1816; Madrepora abdita, Soland. and Ellis, t. 50, f. 2 
66. Genus SIDERASTREA. 
Un parte) Blainville, Dict. des Se. Nat., t. lx, p. 335, 1830; Siderina, Dana, Zooph., p. 218, 1846. 
Corallum incrusting, forming a convex mass of a very dense tissue. Gemmation 
sub-marginal. Cor allites wnited “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. Co/wmella 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 adjoming septa, but are not united to them. Déssepiments rudimentary. 
Typ. sp., Siderastrea galaxea, Blainville, loc. cit. ; Madrepora galawea, 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. Cadices polygonal and 
