ISLE OF MAN. GEOLOGY. LIMESTONE. 555 



every instance filled with calcareous matter, to which 

 rule one very remarkable exception is found. This occurs 

 in the black beds from which the marble formerly de- 

 scribed is procured. Here, the animal remains are all 

 converted into pyrites, while at the same time their 

 forms are more destroyed than in those situations where 

 they are calcareous. It is uncertain whether the vicinity 

 of a considerable trap vein, which traverses the limestone 

 at this place, may have had any influence in producing 

 this change.* 



O 



The unstratified limestone, which accompanies the re- 

 gular beds, is found irregularly interspersed in detached 

 masses throughout the whole calcareous tract, of which 

 it forms a part. It is neither placed above, nor, as might 

 more naturally be expected, below the strata, but is irre- 



* The following list contains a general catalogue of the organic 

 remains which I observed in this rock : 



Pecten three species, but neither of them so perfect as to admit of 

 being determined. 



Madreporitte turbinated ; conical ; ramose with small, and ramose 

 with large stars. 



Orthoceratita. 



Trochita small and large. 



Ammonita the species undescribed ? The shell is smooth, the back 

 flat; the sides longitudinally sulcated, one groove running near the 

 outer edge, and the other, a third larger, running nearly on the middle, 

 but rather towards the outer than the inner edge. 



CorallinittE ramose, flustriform, and straight filiform, resembling 

 those found in the limestone of Dudley. 



Productus. A species of this genus as formed by Sowerby, but not 

 definable. It resembles somewhat the Conchyliolithus (anomites) scabri- 

 culus of Martin. 



Another species, remarkable for the fineness of the striae. 



A turbinated shell, the mouth of which being broken, the genus can- 

 not be ascertained ; but the form of the wreath, and the clavella dis- 

 posed on the upper part of the whirls, and passing off into fine plicae, 

 give it a resemblance to the genus Ceritliium. 



Another turbinated shell, equally obscure. 



Several unassignable bivalves ; besides other fragments so obscure as 

 not to admit even of a conjecture respecting them. 



