John Rofe — Notes on the Crinoidea. 265 



others of considerable thickness. Further, to show that such oscil- 

 lations have taken place, we have evidence that sometimes Crinoids, 

 after partial decomposition, were present and exposed to wind on a 

 sandy shore. Many persons, when walking on the shore of our own 

 coasts, probably may have found the tests of sea-urchins blowing 

 about, partially filled with the fine dry sand of the beach. If these 

 are afterwards blown into a clay or muddy deposit, so coramon in 

 estuaries, they would be filled up with the mud and buried. These, 

 if found hereafter in a raised bed, partially or entirely fossilized, 

 would present much the appearance of Fig. 5, representing the 

 section of a Rhodocrinus, found in a shaly bed in the Mountain Lime- 

 stone at Clithero ; the lower part of the fossil being filled with fine 

 sand (siliceous and calcareous), the upper part with mud very similar 

 to the argillaceous calc-shale of the bed in which it was found : and 

 similar cases are not very uncommon in bivalves and other fossils 

 from these beds. In the Salt Hill Quarry at Clithero there is a thick 

 bed of Crinoidal limestone, composed, as in the beds above named, 

 almost entirely of portions of columns which have evidently been so 

 exposed on a shore and subjected to a similar process. In almost 

 every case the centre of the circular column to which \hQ fihro-carti- 

 laginous process is confined being decomposed and removed, the cavity 

 has been partially, or sometimes entirely, filled up with sand, as in 

 Fig. 6, the fine sand frequently containing, as in the case above 

 alluded to, small portions of the channelled arms and of the minute 

 pinnules or tentacles which fringe the arms of the Crinoid, thus 

 demonstrating the disintegration of these parts of the animal before 

 the columns entirely broke up. That part of the cavity which is not 

 occupied by the sand is often full of transparent calc-spar, 



JVote on Variations in tlie Construction of the Columns. 



In the paper above alluded to, in Vol. VIII. p. 241, of this 

 Magazine, it was stated that a fibro-cartilaginous process ran longi- 

 tudinally along the interior of the column, the rays, and of the side- 

 arms, by which flexibility and the power of regulating the movement 

 were given to these parts, and in illustration sections of a recent 

 Pentacrinus are given, in which the membranes were manifest. It 

 was also stated that the longitudinal fibres were differently disposed 

 in different genera, in some cases surrounding and adjacent to the 

 central canal, and in others in bundles or lobes round the canal, but 

 towards the exterior of the column. The first arrangement appears 

 to apply to round or elliptical, and the second to radiated pentagonal 

 or polygonal columns, irrespective of their geological age. 



In the last volume. Vol. IX., at page 387, Mr. J. E. Lee gives a 

 section of a sub-quadrangular column of a Cupressocriniis from the 

 Devonian formation, very similar in condition to the Chert specimen 

 from the Mountain Limestone (Fig. 8, PI. VT., Vol. VIII.) ; but in the 

 Devonian the cast of the central canal is surrounded by four and 

 sometimes, Mr. Lee states, five smaller columns, as shown in Fig. 3 

 in his paper. These I take to be siliceous pseudomorphs of tlie 

 central canal, and of bundles of fibres similar to those shown in 



