404 



PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [Feb. 29, 



Saurian-beds. The magnificent specimen of Ichthyosaurus platyodon, 

 Conyb., now in tbe British Museum, came from this clay, as proved 

 by the impressions of Am. semicostatus, Y. & B., which are seen on 

 the matrix. This thick clay-bed is underlain by a thin band of 

 greyish limestone, in which Am. Turneri is found. The following 

 section of this zone at Lyme Begis shows the sequence of the Am. 

 Turneri beds at that locality. 



Section of the Zone of Ammonites Turneri at Lyme Regis. 



Organic Eemains. 





Beds 



T„ LlTHOLOGY. 



JNo. 



1. Thick limestone. " Broad 



Ledge" 3 



2. Black shales, with bands 



of brown clay. " Sau- 

 rian- and Fish-bed " 18 



3. Greyish, hard, shelly lime- 



stone 



4. Dark shales, with indu- 



rated bands of imperfect 

 limestone 3 



ft. in. 



Ichthyosaurus platyodon, I. com- 

 munis, Ammonites semicostatus, 

 Am. Turneri, and Fishes. 



Ammonites Turneri and Am. semi- 

 costatus. 



Greyish limestone 



with Am. BucJclandi and Lima. 







Lima gigantea, L. antiquata, 

 Bhynchonella variabilis. 

 (See page 398.) 



and 



Fossils of the Zone of Ammonites Turneri * 

 Conyb. 



Ichthyosaurus platyodon, 



(British Museum). 

 intermedius, Conyb. (Warwick 



Museum). 



communis, Conyb. (Brit. Mus.). 



Ammonites Turneri, Sow. 



- semicostatus, Y. $• B. 



Bonnardi, d' Orb. 



Turbo. 



Lima punctata, Sow. 



gigantea, Sow. 



— — pectinoides, Sow. 



Cardinia ovalis, Stutch. 



Ostrea. 



Avicula, 



Pecten textorius, Schloth. 



— glaber, Hehl. 



Astarte consobrina, Lewal. 



Crenatula. 



Plicatula. 



Gervillia lanceolata, Sow. 



Gryphaea obliqua, Sow. 



Cidaris Edwardsii, Wr. 



Pentacrinus tuberculatus, Miller. 



4. The Zone of Ammonites obtxtsus. 



Synonyms. — " Marston-Marble," Sowerby, Min.Con. Suppl. Index, 

 vol. i. 1812. "Ammonite-bed (Lower Lias)," Murchison, Geol. of 

 Cheltenham, 2nd edit. p. 42, 1845. " Turneri-Thone," Quenstedt, 

 Flozgeb. Wurttembergs, p. 540. " Sable d'Aiibange (pars infer.)," 

 Dewalque et Chapuis, Luxembourg, p. 12. " Gres de Virton (pars 

 infer.)," Dewalque, Lias de Luxembourg, p. 48. " Die Schichten 

 des Ammonites obtusus," Oppel, Juraformation, p. 50. " Indurated 

 marl and limestone-beds,''" De la Beehe, Sections, &c, Geol. Trans. 

 2nd ser. vol. ii. 



Gloucestershire and Warwickshire. — The beds constituting this 

 zone are well developed in the Vale of Gloucester, and were exposed 

 in the deep cuttings of the Bristol and Birmingham Bailway, espe- 

 cially near Bredon, from whence the best collection of the fossils of 



* I have omitted the fossil Fishes found in the Lias at Lyme Begis, as I was 

 unable to ascertain with correctness the beds from which the different species 

 were collected : a- large majority of them, I believe, come from this zone of life. 



