ZONE OF ARIETITES BUCKLANDI. 35 



species appear to be special to the zone of Aeg. angulatum, nearly all of which are repre- 

 sented in the " Gres d'Hettange." 



In Luxembourg the Marne de Jamoigne represents the Angulatum-zone, and beds of 

 the same age are found in the valleys of the Semois, the Chiers, and the Meuse. In 

 Gloucestershire I have seen small specimens, which were found near Aust and Gloucester. 

 This zone is likewise exposed in the north of Ireland, in the remarkable Lias district 

 near Portrush. 



3. The Zone of Arietites Bucklandi. 



Synonyms. — " Blue Lias," William Smith, 'Memoir to the Map,' 1815. " Blue Lias 

 Limestone," De la Beche, ' Geol. Trans.,' 2nd series, vol. ii, 1829. " Gryphiten-Kalk- 

 stein," Alberti, ' Die Gebirge des Konig. Wurttemberg,' p. 121,1826. " Liaskalk," 

 Mandelsloh, 'Geol. Profile der schwabisch. Alpen,' p. 28, 1834. " Calcaire a 

 Gryphites " (pars), Dufrenoy et de Beaumont, ' Mem. Soc. Geol. de Prance,' p. 196, 

 1830. " Gres de Luxembourg " (pars, sup.), Omalius d'Halloy, ' Elem. de Geologie,' 

 p. 375, 1835. "Gres de Luxembourg," Dewalque, 'Descrip. du Lias de la Luxem- 

 bourg,' p. 28, 1857. " Plagiostoma-beds, Lower Lias," Murchison, 'Geol. of 

 Cheltenham,' 2nd ed., p. 49, 1845. " Arietenkalk," Quenstedt, 'Der Jura,' Table, 

 p. 293, 1857. "Die Schichten des Ammonites Bucklandi," Oppel, * Juraformation,' 

 p. 35, 1856. " Zone of Ammonites Bucklandi" Wright, ' Quart. Jour. Geol. Soc.,' vol. xvi, 

 p. 398, 1860. "Zone de 1' Ammonites Bucklandi? Dumortier, 'Etudes Paleont. sur les 

 Depots Jurassiques du Bassin du Rhone,' 2e part, p. 6, 1867. " Die Arietenschichten," 

 Brauns, 'Der untere Jura,' p. 78, 1871. "Zone of Ammonites Bucklandi," Tate and 

 Blake, 'Yorkshire Lias,' p. 54, 1876. 



The Bucklandi-zone forms an important subdivision of the Lower Lias. This 

 series attains a great development in the midland counties and in Glamorgan, 

 Dorset, and Somerset. The rocks are characterised throughout by the prevalence of a 

 number of large Ammonites belonging to the natural group Arietes (von Buch), and 

 by many Lamellibranchiata of the genera Lima and Gryphaa. In England it everywhere 

 consists of beds of grey-bluish argillaceous limestone, interstratified with bands of marl, 

 shale, and clay of a similar colour. In some parts of the counties of Warwick, Somerset, 

 Dorset, and Glamorgan this series attains a thickness of 80 feet. 



Gloucestershire and Somersetshire. — In Gloucestershire it was exposed in the deep 

 cutting of the Dean Forest Railway at Highnam, and is seen in the Lias limestone- 

 quarries near Tewkesbury, and in the natural escarpments at Frethern and Purton-on-the- 

 Severn. In Somersetshire it was sectionised in making the Great Western Railway 

 between Bristol and Bath, and probably at no point were the several beds of the Lima 

 series better shown than in the cutting at Saltford, seven miles from Bristol. My late 



