xl BRITISH FOSSIL CORALS. 



60. Genus Plesiastrea. 



Milne Edw. and J. Haime, Comptes rend., t. xxvii, p. 494, 1848. 



Corallum globose ; its under surface having the form of a naked costulated plate. 

 Gemmation extra-calicular. Calices with a free margin, and a fossula rather shallow. 

 Columella spongy. Pali well developed, and corresponding to all the septa except those 

 of the last cyclum. Septa exsert, formed by a well-developed lamina, and having a deli- 

 cately-serrated apex. Costa and their dissepiments in general well developed. 



Typ. sp., Plesiastrea TJrvillii, Milne Edw. and J. Haime, Ann. des Sc. Nat., vol. x, tab. ix, fig. 2 ; 

 Astrea galaxea, Quoy and Gaim., Voyage de l'Astrolabe, Zooph., pi. xvii, figs. 10-14. 



61. Genus Leptastrea. 



Milne Edw. and J. Haime, Comptes rend., t. xxvii, p. 494, 1848. 



Corallum very dense and incrusting, and increasing by fissiparity, as well as by 

 extra-calicular gemmation. Costal coenenchyma quite compact. Calices in general much 

 crowded together, but preserving their margins distinct. Columella papillose. Septa thin, 

 closely set, exsert, delicately granulated, and having their apical margin almost entire near 

 the walls, but delicately denticulated towards the columella. Dissepiments not very abun- 

 dant. Costa rather indistinct. 



Typ. sp., Leptastrea Roissy ana, Milne Edw. and J. Haime, Ann. Sc. Nat., 3 me serie, vol. x, tab. ix, fig. 6. 



62. Genus Solenastrea. 



Milne Edw. and J. Haime, Comptes rend., t. xxvii, p. 494, 1848. 



Corallum forming in general a convex mass, of a light and cellular structure. Gem- 

 mation extra-calicular. Corallites long, slender, and united by an exothecal structure, 

 and not by the costce, which do not meet, and are often rudimentary. Calices circular, 

 with an exsert margin. Columella spongy, and in general small. Septa very thin ; their 

 margin denticulated. Dissepiments simple, numerous, and closely set. 



Typ. sp., Solenastrea Turonensis, nob. ; Astrea Turonensis, Michelin, Icon., pi. lxxv, figs. 1, 2. 



63. Genus Phym astrea. 



Milne Edw. and J. Haime, Comptes rend., t. xxvii, p. 494, 1848. 



Corallum forming a convex or a horizontal mass. Corallites prismatical ; surrounded 

 from top to bottom by a thin epitheca ; very nearly approximated to each other, but not 

 united by their walls, and cemented together by means of a certain number of large 

 wart-like processes, so as to leave an empty space between them. Gemmation extra- 

 calicular. Calices sub-polygonal, with a free margin. Columella spongy, well developed. 

 Septa large, slightly exsert, and strongly dentated. Walls thick ; no trace of costae. 



Typ. sp., Phymastrea Valenciennmi, Milne Edw. and J. Haime, Ann. Sc. Nat., 3 rae serie, vol. x, 

 tab. ix, fig. 3. 



