I860.] WEIGHT LIAS AND BONE-BED. 389 



or clays are met with, which form a connecting link hetween the ISTew 

 Red Sandstone and the Oolitic systems. These are ahout 17 feet 

 thick. To them succeed alternating heels of dark shale and calcareous 

 grit. 



1. " Compact blackish even shale, or clay, the bottom of which is 

 not seen. 



2. Seam of calcareous grit, about half an inch thick. 



3. Black shale, nine inches. 



4. Seam of calcareous grit, about half an inch thick, but variable ; 

 with impressions of bivalves on one side, and on the other the teeth 

 and scales of Fishes, viz. Saurichthys a/picalis, Gyrolepis Albertii, 

 Gyrolepis tenuistriatus, and Acrodus minimus (Muschelkalk fossils). 



5. Black shale, seven inches. 



6. Calcareous gritty shale, in some parts a calcareous grit, with 

 Bivalves on the faces of lamination ; five inches. 



7. Black shale with Avicula contorta (n. s.) and impressions of 

 Oardium striatulv/m." \C. Hhceticum, Mer.] 



The correlation of these strata with those at Garden Cliff and else- 

 where docs not admit of the shadow of a doubt. 



§ III. The Lower Lias. 

 1. The Zone of Ammonites planoebis. 



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

 p. 47, 1815. " White Lias," De la Bcche, Geol. Trans. 2nd series, 

 vol. ii. p. 26. " Saurian Bods," Murchison's Geology of Cheltenham, 

 2nd cd., by Buckman and Strickland, p. 49, 1S45. "Psilonotenbank," 

 Quenstedt, Der Jura, Table, p. 293, 1857. " Die Schichten des Am- 

 monites planorbis," Oppel, Juraforination, p. 24, 1856. 



This division of the Lower Lias is well developed in the South of 

 England. In general it consists of a series of thin, greyish or bluish, 

 argillaceous limestones, with alternating beds of laminated shale ; or 

 sometimes the entire series forms a thick-bedded, argillaceous, cream- 

 coloured limestone, called " the White Lias" by William Smith. In 

 the upper half of this group of beds Ammonites planorbis, Sow., is 

 found in great numbers, compressed in the shales, with its white 

 shell more or less preserved ; in the lower portion of the series 

 Ostrea /iassicri, Strickl.*, appears in ni-cat numbers; and beneath 

 these strata are three or four beds of hard limestones (or " Eire- 

 stones "), in which the finest skeletons of Enaliosauria have been 

 discovered. As this distinction, by means of Am. plunorhis, Ostrca 

 linssica, and Saurians, is a practical and useful one in the investiga- 



* Ostrea liassiea, Strickland, is a rary characteristic ahell of the Lowest Lias 

 beds. H resembles Ostrea irregularis, fifiinster (G-oldfuss, Petr. Glenn, pi. 7 9. 

 Gg.5)and Ostrea rugata, Quenstedl (Jura, pi. 3. Bg. 17). Dunkerin the'Pahe- 

 (H i ographica' (pl.6. Bg. 27 ) bas figured a small ( lyster from the Liaa of Ealbar- 

 siadi ( Ostrea suolameUosa, Dunker), which appears to be identical with oi 

 raes. These Btnall, thin, rngos. u\.-i<t- arc found in txrent nlutudance in the 

 lowest beds of the Lower Lias in England and Germany. They -.irs probably 

 only varieties oi' one Bpecies, which had a wide geographical distribution in the 

 Beas whi -h deposited the basement-beds of the Lia-. 



