398 PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [Feb. 29, 



Plesiosaurus dolichodeirus, Conyb. 



megacephalus, Stutch. 



Dapedius. 



Pbolidophorus leptocephalus, Ag. 



Stricklandi, Ag. 



Ammonites planorbis, Sow. 



Johnstoni, Sow. 



Lima punctata, Sow. 



gigantea, Sow. 



pectinoides, Sow. 



Cai'dinia crassiuscula, Sow. 

 Unicardium cardioides, Phil. 

 Pdiyncbonella variabilis, Schloth. 

 Cidaris Edwardsii, Wr. 

 Pseudo-diadema lobatum, Wr. 

 Hemipedina Bechei, Brod. 



Bowerbankii, Wr. 



Tomesii, Wr. 



Isastrsea Murchisoni, Wr. 



2. The Zone oe Ammonites Bucklandi, or the Lima-beds. 



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

 " Blue Lias Limestone," De la Beche, Ge'ol. Trans, vol. ii. 2nd series, 

 1829. " Giyphiten-Kalkstein," Alberti, Die Gebirge des Konig. 

 Wiirttemberg, p. 121, 1826. " Liaskalk," Mandelsloh, Geol. Profile 

 der schwabisch. Alpen, p. 28, 1834. "Calcaire a Gryphee arquee" 

 (pars), Dufrenoy et de Beaumont, Mem. Soc. Geol. de France, 1830. 

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

 Luxembourg," Dewalque, Descrip. du Lias de la Luxembourg, p. 28, 

 1857. " Plagiostoma-beds, Lower Lias," Murchison, Geol. of Chel- 

 tenham, 2nd ed. p. 49, 1845. " Arietenkalk," Quenstedt, Der Jura, 

 Table, p. 293, 1857. " Die Schichten des Ammonites Bucklandi," 

 Oppel, Juraformation, p. 35, 1856. 



The zone of Ammonites Bucklandi (or Lima-he&s) forms an im- 

 portant subdivision of the Lower Lias. This series attains a great de- 

 velopment in the Midland Counties, in Glamorganshire, Somerset, and 

 Dorset. This zone of life is characterized throughout by the preva- 

 lence of a number of large Ammonites belonging to the natural group 

 Arietes (von Buch), and by many Conchifera of the genera Lima and 

 Gryphcea. In England it everywhere consists of beds of bluish argil- 

 laceous limestone, interstratified with beds of marl, shale, and clay of 

 a similar colour. In some parts of Warwick, Somerset, Dorset, and 

 Glamorgan, this series attains a thickness of 80 feet. 



Gloucestershire and Somersetshire. — In Gloucestershire it has been 

 chiefly exposed by the deep cutting of the Dean Forest Bailway near 

 Gloucester, in the Lias limestone-quarries near Tewkesbury, and in 

 the natural escarpments at Frethern and Purton-on-the-Severn. In 

 Somersetshire it was admirably exposed 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 friend Mr. William San- 

 ders made the following section during the executiou of the works, 

 which, together with his notes on the fossils contained in the different 

 strata, has been kindly communicated by my friend Mr. Etheridge. 

 This section is of great value, inasmuch as the beds are now partially 

 concealed by debris and vegetation, and the characteristic fossils can 

 no longer be found in their respective beds. 



