408 W. D. Lang— Lower Plienshachian of Charmouth. 



those given in the accompanying diagram. If these are right, the 

 base of the Cretaceous on Stonebarrow is slightly lower than on, 

 Bhick Ven, contrary to Jukes-Browne's surmise. This does not, 

 however, affect the validity of Jukes-lirowne's main argument.' 



It remains to be seen if any correspondence can be established 

 between the sequence given in this paper and the eight subdivisions 

 of the Green Ammonite Beds in the Survey Memoirs. The detailed 

 section given in the Memoirs^ is about 100 feet thick, of which about 

 one-half is occupied with the two lower divisions. It is safe, then, 

 to assume that the five upper Survey divisions are above the Red 

 Band. The upper three of these are remarkable for exhibiting 

 sandy conditions like the Upper Limestone on parts of Stonebarrow ; 

 but they include only 13 feet, whereas the Upper Clay on the west 

 face of Golden Cap is 30 feet thick, and the Upper Limestone should 

 therefore be found towards the bottom of the fourth subdivision of 

 the Survey Memoir, the base of which is 33 feet below the lowest 

 Tier. The 'ferruginous band', the fifth subdivision, is probably 

 a streak of stained clay, since it is 30 feet above where the Red Band 

 should appear. The sixth subdivision contains no hard beds ; and 

 the seventh, of indurated marl and limestone, is admittedly 'occasional' 

 and probably, therefore, local, but might be meant for the Red Band. 

 This leaves the eighth and lowest subdivision, measured with the 

 seventh as 54 feet thick. By measurement this bottom 54 feet should 

 include both the Red Band and the Lower Limestone. The latter, 

 presumably, is the "nodules of hard grey limestone ", though there 

 is nothing in the description that suggests that they are on one 

 horizon ; and the former the ' ferruginous bands ', though, even 

 where the Red Band appears to be double, this would be a poor 

 description of that rock. Thus, even if this interpretation is right, 

 it cannot be said that a satisfactory correlation has been established 

 between the two accounts. 



II. The Belemnite Makls. 



The Belemnite Marls ^ consist of some 80 feet of rock, capped by 

 the Belemnite Stone and bounded beneath by a limestone containing 

 ammonites of the armatiis group. The Survey assign the Marls to 

 the zones of arniafus, jat7ies07ii, and tbex,^ but do not suggest any lines 

 of demarcation; on the contrary, they speak of "an inosculation of 

 the zones''.^ Six subdivisions are given, however, based on the 

 lithic characters of the beds. In practice it is not easy to be sure 

 of these subdivisions, and the following are suggested as easier to 

 recognize in the field (see Diagram III, p. 409) : (1) a lower division, 

 about 40 feet thick, of darker marls — the Lower Marls ; (2) a middle 

 division, about 23 feet thick, of paler marls — the Middle Marls ; and 



' This concerns the general shape of the Cretaceous base-line in this district, 

 see Jukes-Browne, Proc. Dorset Nat. Hist. Ckib, vol. xviii, p. 176, 1897; and 

 Geol. Mag., Dec. IV, Vol. V, p. 164, 1898. 



- The most detailed account is in H. B. Woodward, op. cit., 1893, p. 69. 



^ The Stonebarrow or Belemnite Beds of the Survey Memoirs. 



' H. B. Woodward, op. cit., 1893, p. 67. 



* H. B. Woodward, op. cit., 1893, p. 68. 



