259 



shire, in which part of the country, the asteriae are found in very 

 considerable quantities. 



In the specimen, believed to be from Yorkshire, Plate XVII. Fig, 

 11, which is considerably bowed, the vertebrae have very deep angular 

 recesses between the rays. This specimen is very interesting, since it 

 teaches us a fact respecting these bodies, which is not always pointed 

 out by these fossils. The sides of the vertebrae on the inner sweep 

 which they form, are not above half the thickness which they possess 

 on the outer part : this side of the vertebrae having been evidently 

 compressed by the flexion of the column, during the life of the ani- 

 mal, and whilst capable of having their volume diminished by pres- 

 sure. In the lower vertebra of this column, also may be perceived, 

 the depressions in which the vertebral processes had been attached ; 

 and above this are fifteen vertebrae, in none of which are any marks 

 of similar attachments having existed. 



The column from Yorkshire, Plate XVII. Fig. 6, is deserving of atten- 

 tion on account of the circumstances attendant on its distorted form. 

 Following its flexion with a lens of moderate power, the circumstances 

 on which its flexibility depended, will be immediately perceived. As in 

 the former specimen, so in this, in the inner line of each wave, the 

 vertebrae are evidently thinner than on the outer. In the inner line, 

 the crenated edges of the vertebrae are also seen, most closely pressed 

 into each other; whilst, in the opposite line, they are separated 

 nearly as far as can take place, without absolutely disengaging the ere- 

 nulated edges of the articulating surfaces from each other, at this part. 



This column is composed of three sets of vertebrae, of a larger, 

 smaller, and medium size, thus arranged :- On each side of one of 

 the medium size, is disposed one of the smallest ; beyond each of 

 which is placed one of the largest size. This column is formed of 

 thirty-one vertebrae, on the sixteenth of which, reckoning upwards, 

 are the marks on each of its sides, where the vfertebral processes have 



