SS2 Mr. Webster on some new Varieties of Fossil y^kjoma. 



ternal part is exposed, and corresponds exactly with the smooth cy- 

 linders. Having seen this in one complete instance, I was able to 

 trace it in others ; and was now convinced that the smooth cylinders 

 were only the internal parts of the same body whose various sections 

 formed the white circular and elliptical figures. 



When these forms are enclosed in a very soft sandstone, although 

 the sections are very evident from their colour, yet they are seldom 

 seen in relief, because the cylinders themselves are soon destroyed 

 by the abrasion of the surface ; whereas the hardness of the lime- 

 stone permits them to remain. 



Besides the prodigious quantity of fine specimens of these fossils 

 to be found at the Western lines, PI. 30, there is another circum- 

 stance peculiar to the place, arising from the position of the rocks 

 forming the cliffs. These consist entirely of the green sandstone 

 formation, which ha^ slid down in a mass into the sea at the time 

 when the great failure of the stratum took place which occasioned 

 the under-cliff. The stratification of these rocks dips considerably 

 towards the land, and from the action of the sea on the lower part, 

 large portions have been detached, leaving the upper part over- 

 hanging frequently twenty or thirty feet. These masses have sepa- 

 rated from the rest of the rock, and exhibit in the divisions between 

 the beds a view of their upper and under surfaces. Attached to 

 these surfaces are vast layers of these fossils heaped upon each 

 other, and lying prostrate in every possible direction, and in frag- 

 ments of various sizes. Their substance is always sandstone of 

 very soft quality, and having suffered much from the weather, they 

 appear like sculpture almost defaced. It is not difficult however to 

 trace multitudes both of the stems and heads, varying from four 

 inches in diameter to the eighth of an inch. In the joints between 

 |he beds where they are still not separated, they may also be dis- 



