L. F. Sj a ' — -" "-: \ A . . 



::on, to the surface rocks with which we are acquainted, and 

 inner core which differs in one or both of these charact- 



ly the word "geology" should apply equally to the 

 study of both these regions, but, for convenience and from the 

 limitation of the individual human mind, it is usually confined to 

 the problems presented by the rocks composing the crust, while 

 those of the deeper regions lie outside its scope. 



Such, briefly, are the conclusions which may be drawn from the 

 sciences of terrestrial observation. The statement, I know, is in- 

 complete and imperfeet; some at least of the conclusions will 

 doubtless be traversed and regarded as incompatible with the results 

 obtained from other lines of research, but in their main features of 

 the threefold division of physical condition and the twofold division 

 of chemical composition they seem to me so well founded that the 

 burden of proof lies with those who would traverse, rather than 

 with those who are prepared to accept, them. 



V. — >;:zs : y AmtoyiXES. 

 B- L. F. Spatb B.Se W.G.S 



I. 



' j IHE : jliowing notes were comoiied, for the most part a : _ . Tears 

 J_ ago, but their publication in the present form suggested itself 

 to the writer on the perusal (during a short "leave" from active 

 -T.rice) of a number of recent papers on Ammonites, principally 

 S vinnerton and A. E. Trueman's study of the 

 "Morphology and Li-reiopment of the Ammonite Septum". 1 1 

 main part of that inquiry is devoted to the development of the septum, 

 : ~ -;-.:.--.-_- r -. - : _ -. 7 : 1= - _ \ :::-:- _ : ~- -. . . : : . 

 where sutural development cannot be worked out, "septal sectipns" 

 will to some extent serve as stitute _ze writer lias no 



intention of discussing the usefulness of "septal sections"; but 

 some of the suggestions put forward, and conclusions arrived at, by 

 t 7 \uthors, as well as certain opinions, which they adopt from other 

 workers on Ammonites, invite critical examination. Since, in the 

 present paper, other recent work on the morphology and phye i 

 of the Ammonite septum and suture-line, not yet embodied in t 

 bool- included, and since the writer ventures to put forward 



opinions that differ in many essentials from the views of both 

 textbooks and other authors, it is hoped that the paper may prove 

 of general inte 



Tax Fobwakd Bulge :r rra Sketch:. 

 Swinnerton and Trueman give interesting contoured plans of the 

 second and of the adult septum of Daetylioeeras commune, Sovr~: - 

 and graphs illustrating the average profile of these two septa, and 

 re-tite that "on the whole the second septum tends to be col:: r« 

 rather than convex forwards " d 57), and thai it appears f : ~ e 

 ([adult] septum a3 a whole is convex forward? [ $2). Profeaeoi 



1 Quart. Joum. Geol. So: to .zzJl, pt. i. pp. 25-53. pis. ii-ir, 1317. 



