W. S. Gre&Iey — Boulders in a Coal-seam. 553 



Fig. 9. Ih. Part of the polished caliculnr surface of a specimen showina: the dis- 

 sepiments in the loculi, to which reference is made at page 548, in the 

 description of the genus Rhizmigia. 



,, 10. Rhizanqia elongnta. The synapticulse as they appear in a vertical section. 

 Highly magnified. 



,, 11. lb. A vertical section, showing the dissepiments arranged in irregular 

 layers which are on nearly the same level in all the loculi. They are 

 usually more fused together" than is shown in the figure. Highly magnified. 



,, 12. Pleurosmilia Neocomiennia. The corallum. Natural size. 



,, 13. lb. The calice. Natural size. 



,, 14. BarysmUia Cordieri. A young example. Natural size. , 



,, 15. BarysmUia tuberosa. A young example. Natui'al size. 



IV. — On the Occurrence of Quartzite Boulders in a 



Coal-seam in Leicestershire. 



By W. S. Gresley, F.G.S. 



IN 1883 a scattered group of five boulders was met with in the 

 workings of the Coleorton Colliery in the " Lount Nether" coal, 

 at a depth from the surface of about 375 feet. They were all 

 entirely enveloped in the coal, and occurred about 20 inches from 

 the top of the seam. Four of them were found within a space of 

 20 yards of one another, but no two of them very near together, 

 and the fifth occurred some 500 yards S.W. of the others. The coal- 

 seam was of its normal thickness — namely, about 4| feet. This is 

 the seam marked " Lount 4 " upon the (leol. Survey Sheet No. 46 

 of Horizontal Sections, and it is the lowest but one worked in the 

 district. 



The dimensions and weights of these boulders are : — 



lbs. ozs. 

 5 1 inches shortest diara. 11 8 weight. 

 4i „ ,, 5 4 



4i „ „ 2 10 „ 



3 „ „ 1 10 



„ ,. , If » „ 6| „ 



No two of them are at all alike in outward form, but all are con- 

 siderably, or very much, rounded and smooth-surfaced. No. 1 

 exhibits, very markedly, the divisional planes due to original strati- 

 fication ; these run parallel to its flatter sides. The exterior is rather 

 rough and here and there coated with scaly iron-pyiites and coaly 

 matter, and a very little shale or clay adheres firmly to the boulder, 

 and shows signs of considerable pressure. No. 2 is somewhat pear 

 or wedge-shaped, but is well and smoothly worn all over. No. 3 

 highly rounded into a flattish circular mass, and very smooth all 

 over. When broken through it exhibited a sharp, almost conchoidal 

 fracture, and is evidently extremely compact. No. 4 has a large 

 portion broken away on one side along an original joint (?) ; the 

 edges are now smoothed and rounded off. No. 5 shows a rather 

 singular convex surface, occupying about one-third of its area, which 

 (to me) has the appearance of having been produced by some planing 

 rather than rolling action, but there are no rough or clearly defined 

 edges left; the stri^ (if any really exist) are very minute. I 

 certainly never remember seeing a quartzite pebble of a similar form. 



1. 



7i inches longest diam. 



2. 

 3. 

 4. 

 5. 



n „ 

 43. 



;i " 



^4 J) 5J 



21 



