410 A. It. Hunt — Nomenclature of Ripple- mark . 



of the alveolus, whilst the extent of the uncalcified part increased 

 with each successive layer, but less rapidly than in the typical form, 

 then the removal of the uncalcified portion during fossilization 

 would produce a guard having a more or less funnel-shaped alveolar 

 €nd (Fig. c), of which the apical or posterior portion only would 

 form part of the alveolus, wliilst the anterior part of the cavity 

 would have a greater angle than that of the alveolus or of 

 the phragmocone. This form of alveolar end is illustrated by 

 A. quadralus.^ 



It may also be noted that the alveolar end is frequently less 

 ■dense and more friable than the rest of the guard, having probably 

 been originally less perfectly calcified ; it is therefore easily broken, 

 causing the alveolar end to present the foliaceous appearance by no 

 means uncommonly found in A. qtiadraivs. 



It would therefore seem tliat during the progress of development 

 calcification of the alveolar end extended further and further 

 forward, producing a progressive deepening of the alveolar cavity. 

 This course of development is indicated also by the observations of 

 Dr. Rowe,- who points out that in the examples which he refers to 

 A. granulatus there is a progressive deepening of the alveolar cavity 

 as the Belemnite ascends in the zone. 



VI. — The Descriptive Nomenclature of Ripple-mark. 

 By A. R. Hunt, M.A., F.G.S. 



^VER twenty years ago, in 1882, I ventured to controvert 

 a doctrine which was at the time maintained with remarkable 

 unanimity by all geologists, and which was taught in all the current 

 textbooks. It was that the ordinary ripple-mark of the seashore 

 Avas formed by continuous water-currents of some kind ; the current 

 of water taking the place and performing the office of the current of 

 wind which ripples the surface of sand-dunes. 



As it was a question of authority and textbooks I ventured to 

 join issue with those of perhaps the greatest weight, viz., the 

 series of which several editions were published by Mr. Jukes and 

 Sir Archibald Geikie. I stated my thesis, and the object of my 

 paper, in the following plain words : — 



'' I shall endeavour in the present paper to prove that ripple-marks 

 formed under water are, as a rule, completely independent of the 

 rise and fall of tides, of tidal currents, and of sea beaches ; and that 

 they have little in common with the current-mark, that owes its 

 origin to a continuous current of air or of water" (Proc. Roy. Soc, 

 1882, p. 2). 



* This is the type-species of Bayle's Goniotcidhis. Explication de la carte 

 geologique de la France, publiee par" ordre de M. le Ministre des travaux publics, 

 Tome quatrieme, Atlas, Premiere partie— Fossiles priucipaux des terrains, E. Bayle, 

 1878, pi. sxiii, tigs. 6-8. 



- Proc. Geol. Assoc, vol. xviii, pt. 4 (1904), p. 271, fig. 12. 



