Vol. 50.] ' DEVONIAN ' SERIES IN PENNSYLVANIA. 735 



structures, uormal and inverted, I have failed to perceive ; unless 

 one knows which is which, by actually seeing it and marking it 

 in situ, it is not possible to tell whether a specimen is of inverted 

 cones or not. This remark applies to entire assemblages of conic 

 cakes (e. g. PL XXXV. fig. 1), as well as to separate layers of cones 

 (PI. XXXV. fig. 5). Dr. Ingersoll possesses specimens of cone- 

 in-cone from the Pacific coast, California. These the author has 

 examined, and he sees no material difference between them and the 

 Pennsylvanian Portage cones ; in fact, they are remarkably similar. 



3. Detailed Description of the Cone Formation. 



The largest, best developed, and most perfect individual cones of 

 any separate conic cake are usually found near the centre of the cake. 

 They are surrounded laterally by numerous, more or less scaly or 

 flaky segments of cones, generally arranged concentrically with the 

 larger cones, and wrap round or dovetail into each other, being 

 more and more obliquely inclined towards the bedding-planes as 

 they approach the rim of the disc (see PI. XXXV. figs. 2 & 5), 

 wbere they dwindle down to nothing. Viewed in the direction of 

 the axes of the cones, their apices have a minutely oolitic aspect ; 

 that is, the points of all the cones or parts thereof which occupy or 

 start from the apex-plane of the conic cakes resemble the spotted 

 surface of oolite, though in reality every apex is probably as fine as 

 a pin-point (PI. XXXVI. fig. 20). A characteristic feature of the 

 cone-structures is that the bases of the cones and ' conic scales ' 

 (PI. XXXV. fig. 3) in transverse section reveal a serrated surface 

 (PL XXXV. fig. 5) ; the outer edges of separate conic scales pro- 

 ject a little beyond, as well as over the inner and lower margin of 

 the adjacent scales. But instead of asking the reader to follow 

 closely several pages descriptive of each important detail in the 

 structure of cone-in-cone (most of which details have been described 

 elsewhere by Sorby, Xewberry, Dawson, Young, Cole, Dickinson, 

 Marsh, Mantell, and the author, and are probably more or less 

 well-known or easily accessible to Fellows of this Society), the 

 writer would ask them to carefully study the illustrations which 

 accompany this paper and the explanations annexed to them. With 

 regard to the ' clayey ' or ' dark rings ' of Mr. Young, and the micro- 

 scopical structure of the formation (as the material of the walls of 

 the cones and conic scales may, for convenience, be termed), I 

 would draw the reader's particular attention to PL XXXV. figs. 7, 

 8, 10 and 10 a, and PL XXXVI. figs. 11, 12, 13 and 13 a, and 14. 



Previously to the present writer's first paper on cone-in-cone, 1 no 

 one appears to have studied or published anything relating to the 

 microscopical structure. Mr. Young's specimens do not seem to have 

 revealed anything of it, beyond the clayey rings on the backs of the 

 cones. Prof. G. A. J. Cole, however, 2 observed it and confirms my 



1 Geol. Mag. 1887, p. 17. 



2 Mineralog. Mag. vol. x. (1893) p. 136. 



