200 



an equal portion of whiteness, possess even some degree of transpa- 

 rency. Besides the difference of appearance proceeding from the na- 

 ture of the calcareous impregnation, a considerable difference arises 

 from the combination of other animal remains with those of the 

 encrinus, a circumstance seldom occurring in the Derbyshire or 

 Yorkshire masses. These other animal remains, which nearly equal 

 in quantity the remains of the encrinus, are of the coral kind : 

 chiefly of small, elegant, ramose milleporae, mingled with fragments 

 of the Tubipora Catenulata, and with other marine remains, the na- 

 tures of which are not to be correctly ascertained. Much of this 

 difference of appearance also depends on the different characters of 

 the remains of the encrini themselves, as will appear from the fol- 

 lowing remarks. 



The fragments of the vertebral column are almost all composed of 

 vertebrae which are exceedingly thin, and disposed in a series, in 

 which very thin vertebra alternate with those which are less so, the 

 latter projecting a little beyond the former ; so that the column is 

 transversely ridged in a regular and elegant form, similar to what is 

 represented at Plate XV. Fig. 7. 



The vertebral columns in the specimens I possess, are marked by 

 characters which seem almost certainly to point out a specific dif- 

 ference between the encrinite to which they belong, and those which 

 have been already examined. Extreme thinness of the vertebral tro- 

 chites is a character which, alone, seems to be sufficient to separate 

 the animal of this species from those already noticed ; this property 

 being observable in every part of the vertebral column which I have 

 seen. From a careful examination of the two masses of these remains 

 which I possess, I was much pleased to discover, that the one was 

 chiefly composed of the fragments of ossiculae which had belonged 

 to the superior, whilst the other was almost entirely made up of the 

 remains of the inferior part of the animal. To the investigation of the 

 characters which these possess I now claim your attention. 



