738 MR. W. S. GRESLEY ON CONE-IN-CONE IN THE [Noy. 1 894,. 



EXPLANATION OF PLATES XXXV. & XXXVI. 



[All the specimens, unless otherwise stated, are from the Portage Flags 

 (Devonian ?) of Erie, Pennsylvania.] 



Plate XXXV. 



Fig. 1. Photograph of an exposure of a typical mass of ' cone-in-cone ' in situ in 

 the cliffs of the southern shore of Lake Erie, 2 miles N.E. of the city 

 of Erie, exhibiting a transverse section of the formation occurring near 

 the middle of the Portage Flags. 



Fig. 2. Diagrammatic view of the conic mass in fig. 1, showing the chief charac- 

 teristic features (stratigraphical and structural) of the several layers 

 of cone-in-cone in relation to the central sandstone or nucleal band, 

 above and below which the cones point in opposite directions. 



Fig. 3. A perfect or typical cone ' a,' encircling which are several portions of 

 cone-in-cone structure or conic scales, ' b,' ' c,' ' d,' which shows the 

 relative position of the parts or structure of the formation, as revealed 

 in any one or all of the different layers of cones pervading the conic 

 masses in fig. 2. 



Fig. 4. Portion of a conic cake in contact with, and having tongues or offshoots 

 of, the cone-formation running into the nucleal stratum. 



Fig. 5. Portion of a cake or layer of inverted cone-in-cone, through which 

 passes a thin stratum of dark argillaceous shale between two lighter- 

 coloured layers of similar material, the dark band being thicker where 

 it has become ' cone-in-conized.' 



Fig. 6. Portion of an inverted layer of cones, next to a thin bed of calcareous 

 sandstone : this specimen, on weathering, has split along the bedding- 

 plane separating the cones from the sandy layer. 



Fig. 7. A small portion of the bases of cones and conic scales of a typical layer 

 of the formation, exhibiting the characteristic corrugated or differ- 

 entially wrinkled surfaces, as well as the curvilinear lines which are 

 the divisional planes of the cones. There is also seen a small conical 

 depression, and two or three little conical peaks. 



Fig. 8. Transverse section of cone-material between well -developed cones (not 

 shown), illustrating the wrinkles of the bases of the cones, and the 

 continuation of the wrinkling down the surfaces of the conical 

 hollows in which the cones occur. 



Fig. 9. Perspective view of part of a conic cup (cone removed), showing the 

 differentially wrinkled surface referred to in fig. 8, increasing in size 

 and strength towards the rim. 



Figs. 10 & 10 a. View of a good cone (fig. 10), showing how its surface is ringed 

 horizontally with irregular flounce-like appendages of fibrous cal- 

 careous material, which die away to mere streaks as the apex of the cone 

 is approached. Fig. 10 a shows two of these rings in cross section, 

 magnified about 5 times. 



Fig. 24. One of the numerous dark specks (? an organism) promiscuously scat- 

 tered through the cone-in-cone layers, and seen outside them also 

 (see figs. 7, 15, & 21), magnified 10 times. 



Plate XXXVI. 



Fig. 11. Diagrammatic view through a complete cone, exhibiting the connexion 

 between, or the relative positions of, the corrugated surfaces shown in 

 figs. 7, 8, 9, & 10, and the intervening clayey material (black) en- 

 circling the cone. 



Fig. 12. Enlarged view of a portion of the right side of the conic scales enclosing 

 the cone of fig. 11, showing the feathery or splay-shaped arrangement 

 of cone-in-cone structures lapping around one another, and separated by 

 the calcareous and the non -calcareous rings (see PI. XXX V. fig. 10 a, 

 and the black portions of PI. XXXVI. fig. 11), magnified 4 times. 



Figs. 13 & 13a. Diagrammatic view and plan of base, respectively, of a strong 

 cone, encompassed by typical structure (shown in figs. 7-12 inclusive), 



