W. D. Lang — Lower Plienshachian of Charmouth. 407 



lowest Tier, and about 70 feet above the beach. The only fossil 

 common in this bed is Tragophylloceras loscomhi (James Sowerby). 



Of the four clay masses included within the Green Ammonite 

 Beds, the topmost, the Upper Clay, contains many capricornus-YikQ 

 ammonites, and an Area is fairly common, all in a filmy condition, 

 and small pyritic casts of Tragophylloceras loscomhi (James Sowerby). 

 The second bed, the Upper Red-Band Clay, has similar fossils and 

 in addition pyritic casts of ammonites of the iechei and latcecosta 

 groiips. The third, the Lower Red-Band Clay, in the upper part 

 contains chiefly well-preserved T. loscomhi (James Sowerby) and, 

 rarely, Beroceras davcei (James Sowerby) in films, and, in the lower 

 part, abundant Straparollus of two or three species, other small 

 gastropods, young pyritized T. loscomhi (James Sowerby), and 

 ammonites of the latc&costa group. And the lowest bed, the Lower 

 Clay, fossils similar to those in the lower part of the bed above. 



It should be clear from the above description that there is a con- 

 siderable thinning of the Green Ammonite Beds as they pass westwards.' 

 In fact, at the western end of Stonebarrow their thickness is only 

 half of what it is on the western side of Golden Cap ; while on Black 

 Yen, what remains of them gives evidence of further and proportional 

 thinning. The variation is not, however, quite regular, since at 

 Westhay Water the series appears to be slightly thicker than on the 

 western face of Golden Cap. This diminution affects the whole 

 series equally, so that the thickness of its subdivisions varies directly 

 with that of the whole. Moreover, the Three Tiers share in the 

 diminution, and may be seen on Stonebarrow shorn of half that 

 development they display on Golden Cap.^ The lower two Tiers may 

 be seen in place on Stonebarrow Cliff in the banks bordering the 

 great hollow formed by a fall of the cliff (1908-9) beneath the 

 beeches and pine-trees immediately west of Fairy Dell ; and the Lowest 

 Tier again on the cliff just west of this. The Lowest may be known 

 from the two higher Tiers by being nearly twice as thick (in the 

 same section) as either of these, and far more fosiliferous. Its chief 

 fossils are ammonites of the margaritatus and loscomhi groups and 

 small gastropods. The Tiers are next seen about a hundred yards 

 further east, at the western end of Fairy Dell, just east of the top 

 of a big gully that makes it possible to climb the Belemnite Marls at 

 this point. The gully is blocked in places by large masses of the 

 Lowest Tier. In the section above it all three Tiers were to be seen 

 in place and a few feet of Margaritatus Marls above them. The 

 section, however, during the last year (1912-13) has foundered and 

 is much obscured. The two higher Tiers with Margaritatus Marls 

 above may be seen again beneath the junction of the Lias and Gault 

 in the Lias bank that breaks through the overgrown expanse of 

 Fairy Dell in its eastern part. 



It was conjectured in a former paper ^ that the base of the Cretaceous 

 on Stonebarrow was at about 320 feet O.D. It now appears that 

 this is at least 10 feet too high, and the actual heights are probably 



1 See Geol. Mag., Dec. V, Vol. IX, p. 285, 1912. 



- See Geol. Mag., loc. cit., 1912. 



3 Lang, Geol. Mag., Dec. V, Vol. IV, p. 150, 1907. 



