PLATE IV. 



J. Turbinated madreporite, possessing somewhat of a pyramidal form: remains of 

 its radicle being observable around its lower parts. 



2. A fossil of the same species; but more of a discoidal form. 



3. Another fossil of the same species ; at the lower part of which traces of the root 



like projections are also observable. About the middle of the coral a cleft 

 divides it through about half its diameter : the coral-forming insect having 

 there partly finished his labours and began them a-new. 



4. The stellated surface of a madrepor.te, bearing a very peculiar form. 



5. A turbinated madreporite somewhat resembling Madrepora Cyathus. Linn. 



6. The shirt-button madreporite, (Madrepora Porpita}. Linn. 



7. A turbinated madreporite, the external coat of which having been removed, the 



disposition of its perpendicular lamellae is displayed. 



8. A section of an elongated turbinated madreporite: displaying its tranverse and 



longitudinal lamellae. 



9. A simple madreporite, bearing the form of a compressed cone. 



10. A turbinated madreporite from Gothland : its disk bearing very much the appear- 

 ance of the porpital madreporite. 



H. A turbinated madreporite, apparently of the same species with the former, but of 

 a more conical shape. Fossils resembling this and the preceding specimen 

 are, I believe, frequently found in the island of Sheppy. 



12. Is a cast of calcareous spar, formed in the vacuities of a turbinated madrepore : 

 the remains of the animal having been removed by decomposition. 



1.3. and 14. Two transverse polished sections of a large turbinated madreporite of the 

 species at Fig. 8. The section, Fig. 14, made near to the pedicle, is seen to 

 possess much fewer laminae than the section Fig. 13, which was made where 

 the coral had obtained its full thickness. 



15. A delicately formed turbinated madreporite found in chalk. 



16. A fossil of the same species in chalk. In this specimen the mode of attachment 



peculiar to these animals is shewn, the pedicle of the madreporite being ad- 

 herent to the shell of an echinus. 



IT. Is the section of a piece of Blankenburg marble, in which is imbedded a turbinated 

 madrepore of the species represented, Fig. 1, 2, and 3, 



