1 66 TROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



Ammonites. With regard to the closer approximation of the ultimate 

 to the penultimate septum in the recent Nautilus pompilius, he 

 stronj^ly deprecated the idea that the septa were in any sense movahle, 

 after beinp: once formed, or that it was possible for interseptal shell- 

 growth to take place, thus widening the distance between two septa 

 after their formation. As shell-growth in the Mollusca was identical 

 in method^ whether we dealt with that of the " AVater-Spondylus," 

 with its irregularly-formed septa, or the symmetrically-formed 

 Nmitiliis, he contended that the animal had no more communi- 

 cation with its shell behind the last-formed septum than had the 

 polyp of a tabulated coral power to revisit or alter the portion of 

 its corallum shut off by the last-formed tabula. The constant and 

 steady growth of the shell-lip would, of course, increase the capacity 

 of the body-chamber, and, in the case of the female Nautilus^ this 

 enlargement would be fuUj- occupied hy the fecundated ovary ; but 

 immediately after the extrusion of the eggs, the body would be 

 greatly reduced in size, and a septum would be formed by the 

 animal, to shut off this surplus room, no longer needed by it. In 

 old age, fecundation would cease, shell-growth would go on more 

 slowly, and the latest septa would be closer together. An irregu- 

 larity in the distance apart of the septa, in earlier life, might very 

 well be explained by the (female) animal having accidentally 

 escaped fecundation. Dr. Woodward pointed out that the septa in 

 Mr. Buckman's specimens of Ammonites could not very well be traced, 

 unless sections were made. 



Mr. E. T. lN"EWToif read Mr. Buckman's reply from a letter which 

 he had received : — 



" It seems to me a very easy way to dispose of adverse facts 

 to say that the specimens must be prematurely aged or suffering 

 from disease. So far, however, as I remember the specimens 

 exhibited, they do not show signs of old age or disease, such as lop- 

 sided coiling, malformed ribs, carina obsolete or to one side, partially 

 obsolete ribs, &c. As to the disease part of the theory, I send you 

 a specimen of Am. suhplanicosta^ lopsided and rather abnormally 

 grown, in which the septa are striking^ farther apart than those of 

 normally grown examples — a fact totally opposed to Mr. Bather's 

 last contention. The specimens which I have exhibited seem to 

 show that the suture-line was, in some manner, moved forwards 

 after it was formed. To sweep these specimens all aside by saying 

 they are abnormal seems to be begging the question : it is equivalent 

 to stating that all specimens which do not fit a preconceived theory 

 are therefore necessarily abnormal." 



2. " On the Drifts of Flamborough Head." By G. W. Lamplugh, 

 Esq., F.G.S. 



3. " On a Phosphatic Chalk with BelemniteUa quadrata at 

 Taplow." By A. Strahan, Esq., M.A., P.G.S. (Communicated by 

 permission of the Director-General of the Geological Survey.) 



