410 W. D. Lang — Lower Plieiisbachian of Charinouth. 



(3) the Upper Marls, on the whole darker than the Middle Marls, 

 about 16 feet thick. 



The Lower Marls have at their base the Arniatus Limestone just 

 mentioned. This rock is rarely exposed on Black Ven and on the 

 M'estern end of Stonebarrow, being generally covered with talus ; 

 but it is well shown at the base of the eastern part of Stonebarrow 

 Cliff where it comes down to the beach about a mile east of the moiith 

 of the Char ; and it forms a long ledge under the shingle bank between 

 the tide-marks still further east, that is more or less exposed according 

 to the accidents of wave and shingle. It is the home of the "large 

 examples of this Ammonite \_^Derocerasarmatimi\ with prominent spines" 

 whose "particular horizon requires investigation" of the Survey 

 Memoir.^ The ammonites are poorly preserved, being repi'esented 

 only by a black film, and, since the matrix is comparatively liard, 

 they are difficult to extract satisfactorily. The Armatus Limestone 

 lies a foot or two above the Watch Ammonite Stone (the " Grey, 

 earthy limestone " of the 1893 Memoir, and part of the " Watch-stone 

 Beds" of the later Memoirs), a characteristic Limestone often crowded 

 with Ammonites of the raricostahis group. At the base of the Lower 

 Marls, and extending to within a foot of the Armatus Limestone, are 

 one or two pale bands that look like Limestone. They can hardly, 

 however, rank as such, being merely indurated marls, and, although 

 highly calcareous, are quite soft compared with the Armatus Limestone. 

 In fact, there is no definite bed from the Armatus Limestone up to 

 the Belemnite Stone that is anything more than an indurated marl. 

 If these are the " marly limestones and shales " constituting the last 

 two subdivisions of the Belemnite Marls in the Survey Memoirs, the 

 Armatus Limestone is not there recognized.^ It is better, however, 

 to regard these lowest two subdivisions as including the Armatus 

 Limestone and the pale indurated marls above. These pale indurated 

 marls at the base of the Lower Marls must have some wave-resisting 

 quality in spite of their comparative softness, for they form the shoal 

 called Hawkfish Ledge that lies just off Westhay Water. Owing to 

 the change of the dip here from an easterly direction to nearly 

 horizontal, this ledge, instead of running out seawards at a small 

 angle with the coast, swings round festoon-wise, enclosing a minute 

 roadstead at half-tide. The Armatus Limestone does not appear to 

 form part of Hawkfish Ledge, but makes a reef running seawards of 

 it. Except for the lowest few feet the Lower Marls are dark as 

 a whole and comparatively barren. They yield belemnites and 

 saurian remains, and, at the top, the same Inoceramus as the Middle 

 Marls. If, as is possible, the Middle Marls represent the jamesoni 

 zone, it is likely that the rare examples of A. pettos that have been 

 found beneath Stonebarrow Cliff come from the Lower Marls. 



The Middle Marls consist of three thicker pale and three thinner 

 dark bands. The pale bands are very fossiliferous in places, though 



^ Woodward & Ussher, op. cit., 1911, p. 30. 



■ The Survey follow Day in calling these indurated marls, limestones ; see 

 Day, Quart. Journ. Geol. Soc, vol. xix, p. 281, 1863. On p. 280, however. 

 Day speaks of "semi-indurated limestone", which is a far less misleading 

 description. 



