259 
shire, in which part of the country, the asteriae are found in very con- 
siderable 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 animal, 
and whilst capable of having their volume diminished by pressure. 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 crenulated 
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 lai'gest 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 vertebral processes have 
