199 



Plate XV. Fig. 3, is the representation of a specimen of the York- 

 shire entrochal marble, in which the organic remains are very beau- 

 tifully disposed in relief on its surface. As I have already remarked, 

 I am unable to discover any essential difference between the entrochi 

 existing in the Yorkshire and in the Derbyshire marble. Those in the 

 Yorkshire marble seem, however, to be generally smaller, and of a neater 

 conformation than those in the marble of Derbyshire ; but whether 

 this proceeds from real difference of species cannot, perhaps, be 

 determined from such specimens only as I have had the opportunity 

 of seeing. The colour, in different specimens of the Derbyshire and 

 Yorkshire marbles, varies much from a light to a dark brown. This 

 specimen is of the latter hue. 



Plate XV. Fig. 2, represents a polished specimen of this marble, 

 formed of the mineralized remains of separated columns of trochital 

 vertebrae. By attention to the different sections of these columns, a 

 tolerably correct knowledge of their construction will be obtained ; 

 remembering, that the lighter parts are the remains of the original 

 animal substance, and that the darker is the interposed crystalline 

 matter. 



From the observations which I have been able to make on the re- 

 mains of the encrinus in the limestone, or rather marble, of Wen- 

 lock Edge, in Shropshire, I am fully satisfied that it is a species dif- 

 ferent from both the lily encrinite and the cap encrinite of Derby- 

 shire. My reasons for forming this conclusion, I shall now offer to. 

 your consideration. 



The calcareous masses of the remains ofencrini which are obtained 

 from Wenlock, possess certain characters which immediately distin- 

 guish them from such masses of entrochal marble as are obtained 

 from any other part. The organic remains themselves are formed of 

 calcareous matter, which being apparently very free from any ferrugi- 

 nous impregnation, is nearly white ; and hence the organic remains 

 are, some of them, beautifully white and opaque ; whilst others, with 



