ZONE OF HARPOCERAS BIFRONS. 127 



Gasterotoda. 



Eucyclus capitaneus, Milnst. 

 Trochus bisertns, Phil. 

 Cerithium, sp. 



Pleurotomaria subdecorata, Milnst. 

 Rostellaria, sp. 

 Natica, sp. 



14. Zone op Harfoceras bifrons. 



Sj/?iofit/ms. — "J. communis-hed," part, Wright, ' Quart. Journ. Geol, Soc./ vol. xiv, 

 p. 25, 1858. " Zone of J7n. communis," part, Wright, 'Oolitic Asteroidea,' Palffiont. 

 See, p. 38, 1862. " Zone a Jm. bifrons" Reynes, ' Geol. et Paleont. Aveyron,' p. 65, 

 1868. " Zef/a-oy«;«-beds," Judd, " Geol. of Rutland," ' Mem. Geol. Surv./ p. SO, 1876. 

 "Zone of Am. communis or Alum-shale" Tate and Blake, 'Yorkshire Lias,' p. 181, 

 1876. 



This zone at Frocester Hill consists of tine sandy marls, with inconstant bands of a 

 harder sand rock, which form several layers of nodules in the bank, and many of these 

 contain fossils. I have found sometimes clusters of Harpoceras bifrons in some of these 

 masse* when broken up — a fact which first taught me the true stratigraphical position of 

 Harp, bifrons. Along other escarpments of the Cotteswolds I have collected Harp, 

 bifrons in brownish marl at the southern base of Crickley Hill, and in soft grey clays 

 above the Serpcntinum-heA at Stinchcombe Hill. 



In the Saltwick profile near Whitby, and at Rock Cliff, near Staithes, on the York- 

 shire coast, we have already seen that Harp, bifrons belongs to the alum-shale, and has 

 for its associates Stephan. commune, Belemnites VoUzii, Leda ovum, and Gresslya donaci- 

 formis, and that it there forms a well-marked horizon of life resting upon the Jet-rock, 

 with Harpoceras serpenlinum, and Harp, falcijerum. 



On cutting the eastern portion of the Banbury and Cheltenham Direct Railway some 

 instructive sections of the Upper Lias have been exposed onnearing Bloxam, Oxfordshire. 

 Mr. Beesley^ notes, " about 300 yards before reaching the Barford-road Bridge, a small fault 

 brings down the Upper Lias about four feet against the 8pinatus-\>Qd&. For 100 yards 

 further the banks are all Marlstone of this zone ; then comes another fault, dipping to the 

 east, which throvt-s down the Upper Lias to the base of the section, a depth of fifteen feet ; 

 the white marly limestone of the Serpentinum-hQ^s,, crowded with Harpoceras bifrons, 

 Stephanoceras commune, Lytoceras cornucopice, Phylloceras heterophyllum, Phyll. subcarina- 

 tum, and species of the Serpentinum group, with Belemnites llminsterensis and B. regularis 

 and Nautili, now forming the floor of the line, and over it blue or green shale fifteen feet 

 thick. The faults pass obliquely across the line from north-west to south-east." 



1 "Geology of the Banbury and Cheltenham Railway," ' Proc. Geol. .\ssoc.,' vol. 7, 1877. 



