442) A POPULAR EXPOSITION OF THE 
They have formed the nuclei, to which, during the consolidation of 
the strata, much of the cherty matter has been attracted. In some 
of the silicified corals and brachiopods, petroleum is also found. 
A. few of the ‘more important organic remains are shown in the 
annexed figures :— 
ie 
E | 
Fig, 228. Fig. 229, Fig. 230. 
Michelinea convera Syringopora Maclurei Zaphrentis prolifica: 
(D’Orbigny). (Billings). (Billings). 
Fig. 231. Fig. 239. Fig. 233. 
Cystiphyllum Senecaense Strophomena rhomboidalis Spirifer gregarius 
(Billings). (Wahlenberg). (Hall). 
Vig. 234, 
Athyris Clara Pentamerus aratus 
(Billings). (Conrad). 
