392 PROCEEDINGS OE THE GEOLOGICAL SOCIETY. [Feb. 29, 



Modiola minima, Sow., M. psilonoii, Quenst., Gervillia, n. sp., Ano- 

 mya, n. sp., Myacites, n. sp., Area, n. sp., and Cardimn, n. sp., are the 

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



This section likewise settles a point which has been often disenssed, 

 namely, what is the age of the Saurian beds of Somerset ? It has 

 been generally supposed that they belonged to the same horizon as 

 the lower Saurian beds at Lyme Regis ; but this is a mistake, inas- 

 much as the Saurian beds at Street belong to the zone of Ammonites 

 planorbis, most of the reptiles having been contemporaries with that 

 Cephalopod. I am aware that this conclusion is somewhat in oppo- 

 sition to the generally received opinion upon the subject ; but there 

 cannot be a doubt of its truth, as it admits of the clearest demon- 

 stration. The Saurians of Lyme Eegis, on the contrary, are for the 

 most part found in beds above the zone of Ammonites BucMandi, as 

 we shall learn when I describe the fauna of that zone (see page 402). 



Worcestershire and Gloucestershire. — The Am. planorbis, Ostrea, 

 and lower Saurian beds, so well developed at Street, are likewise 

 found in different parts of Worcestershire and Gloucestershire, where 

 they present the same stratigraphieal relations, and yield the same 

 organic remains. 



The neighbourhood of Tewkesbury affords several good exposures 

 of the infra -ammonite beds. I have obtained Ichthyosaurus tenui- 

 rostris, Conyb., and Ichthyosaurus intermedins, Conyb.,from a bed of 

 light- cokrarecl Lias at Haselgrove near " the Folly ; " and the late 

 Mr. Dudfield, of Tewkesbury, collected several very fine skeletons of 

 Ichthyosaurus tenuirostris, Conyb., /. intermedins, Conyb., and I. com- 

 munis (?), Conyb., with bones of Plesiosaurus Haivlcinsii, at Brocke- 

 ridge Common, and from similar beds at other localities around 

 Tewkesbury ; and I possess several vertebrae of Plesiosaurus rugosus, 

 Owen, which were obtained from a bed of "White Lias at Woohidge 

 near Hartpury. 



The junction of the Lower Lias with the red marls of the Keuper 

 in the Yale of Gloucester is, in general, indicated by a low escarp- 

 ment, which faces the west. At Brockeridge and Defford Commons 

 this natural boundary is exceedingly well marked, and between 

 these two localities there are several quarries which expose to a 

 greater or less extent the beds now under consideration. The pre- 

 sence of Ammonites planorbis in the upper strata of several of these 

 sections has enabled me to correlate the beds beneath with the cor- 

 responding strata at Street, in Somerset, and at Binton, Grafton, and 

 Wilmcote, in Warwickshire. 



