TRANSACTIONS OF SECTION K. 747 



where marine shells are found in the shaly roof of the seam. Stur has also noticed 

 the same in the case of calcareous concretions (Sphserosideriten) in certain Aus- 

 trian coal seams. These are accompanied by roof nodules (Thon-Sphserosideriten) 

 containing the remains of marine shells. 



On the other band Mr. James Lomax has pointed out that when the calcareous 

 nodules are very numerous, and often welded together into a single mass, neigh- 

 bouring nodules do not show continuity of plant structure ; which fact he suggests 

 points to the possibility of the nodules having been carried into their present posi- 

 tion after petrifaction. 



To settle definitely which is the mode of formation it would seem important : 



(1) To obtain as much evidence as possible from a wide geographical area, and 

 from difierent horizons, of the occurrence of these calcareous coucretions in coal- 

 seams, and to note whether they are in all cases associated with a shale roof con- 

 taining remains of marine animals. 



(2) To examine carefully the tissues in closely packed nodules, with a view to 

 discovering any possible continuity of structure, so as to determine whether the 

 nodules have been formed m situ or not. 



3. On the ' Coal-Balls 'found in Coal Seams. 

 By Miss M. C. Stopes, B.Sc, Ph.D. 



Owing to the variety of concretions and nodules found in the Goal Measures, 

 and the many local names for them, it seems wise to describe those distinct con- 

 cretions in the actual seam, containing plant structures and now well known to 

 botanists, as ' coal-balls ' ; and the concretions in the roof above them containing 

 goniatites and a few plants, as ' roof-' or ' goniatite-nodules.' 



For long it has been generally accepted by those who work among the Lower 

 Coal Measures that the true coal-balls are to be found only in one geological 

 horizon — viz., the ' Bullion,' or 'Upper Foot ' Mine. 



In the course of our work, however, Mr. Watson and I have satisfied ourselves 

 that (granted the correctness of H.M. Survey of the district, which in this case 

 seems beyond doubt) a seam containing typical coal-balls associated with goniatite 

 nodules, which we have unearthed, lies some distance beloiv the well-known 

 Gannister bed, while the true Bullion seam lies above it. The pit at Hough Hill 

 which has supplied so much material seems also to belong to this lower horizon. 



Further, I have evidence of very similar, if not identical, structures in the 

 Middle Coal Measures. This shows that the factors needed for the formation of 

 these structures have combined more than once during the deposition of the Coal 

 Measures as a whole. 



The coal-balls are undoubtedly concretions, largely composed of CaCOj, though 

 varying much locally, as detailed analysis shows. They are of various sizes and 

 often completely surrounded by coal. As a rule the plants in two neighbouring 

 balls are disconnected fragments, but in some cases the same plant continues in 

 two nodules. This suggests that the concretions containing the plant tissues were 

 formed in the place in which they are now found (except for slight subsequent 

 shifting due to earth movements). 



Though this is opposed to Mr. Lomax's view, it seems to be supported by the 

 discovery at Shore of a single calcareous mass, in the form of a number of nodules 

 cemented together by carbonates, all rich in preserved plant remains ; the whole 

 enormous mass weighing two tons and locally re)>lacing the coal in the seara. 

 While further in support of the in situ theory, a coal-ball found in the floor of the 

 seam contains practically nothing but stigmarian rootlets. 



The constant association with the roof nodules containing marine shells suggests 

 that the infiltration of sea-water and carbonate was necessary for the formation cf 

 the true ' coal-balls,' a view suggested by Binney ; against which we have as yet 

 discovered nothing directly militating, though we cannot give conclusive facts in 

 its favour. 



A careful survey of the mine at Shore reveals the extremely local occurrence 



