ZONE OF AEGOCERAS PLANORBIS. 



17 



No. 



27 



28 

 29 



30 



31 



LlTHOLOGY AND LOCAL NAMES OP BEDS. 



Thin-bedded limestone. ''Three-inch 

 blue bed " 



Thick blue limestone 



Hard fine-grained limestone. " Fire- 

 stone" 



Hard, grey, fine-grained limestone 



Hard grey limestone. " Fire-stone, 

 bottom bed " 



Thick- 



ness. 



ft. 



in. 







3 







.5 







4 







4 



I 







Organic Remains. 



Fish remains, Modiola minima and Otopteris acu- 

 minata. L. & H. 



Plesiosaurus Etheridgii. (In Jermyn Street Mu- 

 seum ; and another in Street are from this bed.) 



Plesiosaurus Hawkinsii. [The large Pies, mega- 

 cephulvs, Stutch., now in the Bristol Institution, 

 was obtained from this bed near Street.] 



The Saurian beds near Langport have likewise yielded Reptilian remains. I obtained 

 two fine specimens of Ichthyosaurus intermedins and an imperfect specimen of I. tenui- 

 rostris from this locality ; the former is now in the Collection of the Earl of Ducie. In 

 connection with the Saurian beds of Somerset, it is important to note that the oldest 

 Enaliosauria of the Lias are Plesiosaurus Hawkinsii, Owen, and PI. Etheridgii, Huxley, 

 which were both exhumed from the 4-inch firestone, forming the bottom bed of the 

 Ostrea-series ; the remarkable Plesiosaurus megacephalus, Stutch., now in the Bristol 

 Museum, was likewise found in the firestones of a quarry near Street Eoss ; and it will be 

 shown in my section of the correlative beds of this zone at Wilmcote, in Warwickshire, 

 that the fine skeleton of Plesiosaurus megacephalus contained in the Warwick Museum 

 was also exhumed from the " firestones " of that locality — beds Avhich are the true 

 equivalents of the "firestones '' of Street. 



The small number of Lamellibrancldala hitherto found in these beds is very 

 remarkable. Ostrea liassica, Strickl., 0. irregularis, Quenst., Modiola minima, Goldf., 

 M. psilonoti, Quenst., Gervillia Hagenovii, Dunk., Anomya striatula, Opp., Pleuromya 

 Crowcombeia, Mor., Macrodon Hettangiensis, Terq., and Protocardia Phillijjpiana, Dunk., 

 are the only species I have as yet collected from the firestone-beds. 



This section likewise settles a question which has been often discussed, namely, what is 

 the age of the Saurian beds of Somersetshire ? It has been supposed that they appertain to 

 the same horizon as the lower Saurian beds at Lyme Regis, Dorsetshire ; this, however, 

 is a mistake, inasmuch as the Saurian beds at Street belong to the zone of Aegoceras 

 planorbis, whilst the Saurian remains at Lyme Regis, on the contrary, are for the most 

 part found in and above the zone oi-Arietites BucJdandi. 



Worcestershire and Gloucestershire. — The Planorbis-, Ostrea-, and Saurian-heds so 

 well developed at Street, are likewise found in different parts of Worcestershire and 

 Gloucestershire, where they present the same stratigraphical relations, and yield the same 

 organic remains. 



The neighbourhood of Tewkesbury affords several good exposures of these infra- 

 ammonite beds. I have obtained Ichthyosaurus tenuirostris, Conyb., and Ichthyosaurus 



3 



