20 TF. S. Gresley — On " Cone-in- Cone " Structure. 



a double cone-in-cone development on the surfaces of a large crack 

 or cavity in the side of the specimen ; whilst at c, in the interior of 

 the same nodule, occurs a small and rather feeble development of 

 the same structure, in no way connected with the top and bottom 

 cone-in-cone layers. Again, as the band marked h h, which is a layer 

 of three or four inches of argillaceous ironstone, is crowded with 

 well-preserved leaflets of Neuropteris gigantea, surely these organic 

 remains must have greatly suffered had contraction of the mass taken 

 place to any extent, which is not the case. 



(c) Very good hand-samples of whole disc-shaped clay-ironstone 

 nodules, exhibiting on both flat surfaces well-formed cone-in-cone 

 structure, are preserved in the Geological Museum of Owens College, 

 Manchester, and here again we find that this structure is much more 

 strongly developed on one side than on the other, and that the coned 

 surfaces are confined to the central parts of the nodules, as shown 

 in Fig. 3, which is roughly half the size of the Manchester specimens. 

 As these nodules were not labelled, I cannot give their locality, etc. 



(cl) In the Museum of the Yorkshire College of Science, Leeds, 

 there is a small specimen of earthy limestone from the Wealden 

 beds, Brixton Bay, Isle of Wight, upon whose upper and lower 

 surfaces cone-in-cone formation is seen — very minute upon the 

 underside — the upper one commencing in contact with a layer of 

 fossil bivalve shells whose uneven surface corresponds with that of 

 the apices of the cones. 



(e) I have quite recently noticed in the shale " baring " of the fire- 

 clay opencast workings in the Leicestershire Coal-field singular 

 nodular masses of hard flinty fine-grained stone (a worthless variety 

 of clay-ironstone), one of which is shown 

 in cross-section in Fig. 4. Upon the sur- 

 face of this specimen the cone-structure 

 has the appearance of having been sub- 

 jected to considerable shrinkage, as the 

 cones or rather wedge-shaped scales of 

 cone-in-cone structure, occur in curious 

 wrinkles or ridges upon the general sur- 

 face of the stone. As these singular ex- 

 amples were not seen in situ, I cannot say 

 which sides were uppermost in the shale. 



(/) Again, occurring in the same stratum are some large concre- 

 tionary somewhat tabular-shaped masses of the same kind of rock as 

 that last noticed, and having a kind of clay-ironstone band running 

 through their centres (see Fig. 5). These nodules are sometimes 

 soA^eral tons in weight. Now, forming the entire upper and lower 

 portions of these singular stones ai-e cone-in-cone structures as shown 

 in the sketch ; and occupying zones lying between the cone-in-cone 

 portions and the rather sharp edges or peripheries of the masses, both 

 upon upper and loioer surfaces, are formations of innumerable little 

 spheres or spherulitic concretionary masses, and, as it were, grown 

 together, — very perfect and distinct upon the surface, but raj)idly 

 dying out towards the interior of the stone, and apparently grading 



