LETTER IX. 



MADREPORA STELLATA, &C M. TRUNCATA M. STELLARIS 



MADREPORITE FROM STEEPLE ASHTON.... MADREPORA ORGANUM, 



&C M. FLEXUOSA M. FASCICULARIS M. PECTINATA M. 



ARACHNO1DES...M. VERMICULAR1S...COR ALLOJDE A COLUMNARIA 



PENTAEDRA OF WOODWARD MADREPORITE FROM INGLEBO- 



ROUGH JUNCI LAPIDEI KILKENNY MARBLE. 



X HAVE had no opportunity of ascertaining whether madrepora stel- 

 lata, m.punctata, m. calycularis, m. nodularis, m. acropora, or m. cavernosa, 

 are known in a mineralized state. 



Madrepora truncata, Plate V. Fig. 2, which is not at all, I believe, 

 known in a recent state, is an exceedingly interesting fossil; not merely 

 from its beautiful appearance, but from its curious mode of increase. 

 It is a proliferous madrepore, and is formed of cyathiform bodies, pos- 

 sessing a superior stellated flat surface, with a concave central depres- 

 sion. From the flat surrounding surface of the stars, smaller stellated 

 bodies proceed, possessing the same form and the same proliferous 

 property. 



The form of the star in this madrepore is remarkably elegant. It is 

 composed of sometimes sixty lamellae; thirty of which commence at 

 the edge of the star, and proceed about half way towards the centre, 

 when they descend perpendicularly, and then, at a certain depth, turn 

 at a right angle, and converge to the centre of the disk; thus forming, in 

 the centre of the star, a cylindrical cavity with a flat bottom. The other 

 thirty of the lamellae are shorter, and proceed only halfway, that is, to 

 the commencement of the central cavity. The termination of these at 



