Clifton College Scientific Society. 73 



below is placed by some in the lias, above which it rests, but from 

 the nature and appearance of the fossils I consider it to belong to 

 the oolite. It is seldom found ; one portion crops out in the 

 fernery of one private house, and another close by the gate of a 

 second. The fossils are mostly ammonites, with a few terebratulce. 

 Close by this sand is a dislodged bed of the clay, which is con- 

 stantly falling down. In it rise several springs. One, which is in 

 the garden of a private house, is an encrusting well. These are 

 usually called petrifying wells, but that is a mistake ; the water 

 has not the property of turning the leaves, twigs, and such bodies 

 into stone, but merely covers tliem with a coating of tlie mineral 

 which it holds in solution. The great oolite contains, besides the 

 fossils above enumerated, several echinodermata — cidarites and 

 echinobrissi — and several spines, but these latter are always de- 

 tached, and a considerable distance from the rest of the fossil. The 

 echinites are often covered with papilhie, which fit into cavities at 

 the base of the spines, which are only supported by the capsular 

 envelopment of the common covering ; but in some cases the large 

 spines are attached by a ligament passing from the centre of the 

 socket, which is received in a perforation in the papilla. The 

 spines present a cellular structure, and when large enough to be 

 divided, form excellent objects for microscopic slides. Many of 

 the specimens from the oolite are of the flat kind, called clypei, 

 but these are not so common as the rest. 



Another interesting class of fossils obtained from the great 

 oolite is the family of the Crinoidce. These remarkable remains 

 are found as early as the Silurian, but are not often found above 

 the oolite. The most i^erfect are obtained from the lias, seldom 

 more than ossicula and portions of the column being obtained 

 higher up. These detached osselets are called entrochi. The two 

 commonest species are pentacrinite and encrinite ; a third, called 

 apiocrinite, is found in the Bradford clay, of which there are 

 excellent specimens in the British Museum. The ossicula, of 

 which the skeletons of all these animals were composed, resemble 

 those of the starfish ; their use was to form a solid support for 

 the body to protect the viscera, and to form the foundation of a 

 system of contractile fibres which ran through the whole animal. 

 The bony portions formed the great bulk of the animal, as they 

 do in starfishes. The calcareous matter of these little bones was 

 probably secreted by a periosteum, which in cases of accident, to 

 which bodies of such delicate structure must have been particu- 

 larly exposed, seems to have had the power of repairing injuries. 

 The number of bones in these animals is astonishing, as many 

 as 26,000 have been counted in an encrinite, irrespective of the 

 column by which it was attached to the rocks : — 20 bones in the 



