74 Transactions of the 



cup part of the animal ; 10 arms, with 6 bones in each arm ; 

 hands — each hand has two fingers, each of which consists of at 

 least 40 ossicula, these, iu 20 fingers, give 800 ; tentacula, 30 

 proceeding from each of the 6 bones in each of the 10 arms, 

 1800 ; 30 proceeding from each of 800 bones of the fingers, 

 24,000— total, 26,000. It has been observed that this number 

 would be immensely increased if the minute calcareous plates that 

 are woven into the integument of the abdomen could be taken 

 into account. All these parts are piled on the top of a slender 

 shaft, which consists of innumerable joints, and is possessed of a 

 high degree of flexibility. To give the requisite amount of flexi- 

 bility, the joints present an extremely varied appearance, both in 

 external and internal forms and dimensions. Tiie column is 

 attached to the ground by an enlargement of the base ; the joints 

 articulate firmly with each other ; there is an aperture through the 

 midst with a small alimentary cavity descending from the body to 

 the base. Pentacrinites, which appear to be allied to the star- 

 fislies, abound in the lower beds of the oolite and in the lias. The 

 upper portion of the vertebral column is constructed like that of 

 the encrinite ; all the joints present a pentagonal starlike form, 

 whence their name of starstones or asterite ; the surfaces were 

 covered by lines of minute teeth, locking into the interstices on 

 the corresponding surface of the next vertebra, and so disposed 

 as to admit flexure in all directions, without risk of dislocation. 

 The columnar joints of P. Briareus are disposed in pieces alter- 

 nately thicker and thinner, with a still thinner joint between them. 

 As the root was usually fixed to the bottom of the sea, or some body 

 floating in it, the jointed column had to change the position of 

 the body either for food or to yield to the direction of the cur- 

 rents ; the root was probably slight and easily withdrawn from 

 the ground to which it was attached. The absence of large solid 

 secretions, like those of the apiocrinites, by which the pentacrinite 

 could have been fixed permanently to the ground, and the fact 

 that it is found in contact with drifted portions of wood which 

 are converted into jet, tend to prove that it was a locomotive 

 animal, with the power of attaching itself temporarily to extrane- 

 ous floating bodies or rocks at the bottom of the sea, either by its 

 side arms or the small articulated root. The side arms gradually 

 become smaller towards the top of the column, and sometimes 

 number about 4000. These, when expanded, would act as nets to 

 hold the prey or help to keep the animal to its hold on the rocks, 

 &c. In rough water they would close and fold up along the 

 column in such a position as to expose the least possible surface. 

 The abdominal cavity is rarely preserved in its fossil state, but 

 it formed a funnel-shaped pouch of considerable size, composed 



