85 



Southerndown Mollusca are peculiar to a definite horizon, and 

 but a few species pass upwards " into the Ammonites Bucklandi 

 zone. " The Sutton stone, with its superimposed Southerndown 

 beds," he regards as " forming one palseontological series," and 

 as *' the representatives and equivalents, lithologically and 

 palseontologically, and in a positive as well as in a differential 

 sense, of the beds included in the zones of Ammonites angulatus 

 and Ammonites Moreanus — the Hettangian." Finally he includes 

 under the term Infra- Lias all the beds between the Ammonites 

 BucJclandi zone, or the true Lias, and the Keuper. He further 

 divides the Infra-Lias into three zones — an upper, middle, and 

 lower. In the upper, he places the Sutton and Southerndown 

 group. In the middle, the Ammonites planorbis zone of Weight, 

 and pai't of the White Lias. In the lower bed, he places the 

 remainder of the White Lias, the Avicula contorta beds, and 

 the Keuper; this last zone corresponding with the Rhsetic of 

 Moore. 



Since the publication of the paper by Mr. Duncan above 

 referred to, a very long and elaborate notice of these beds has 

 been read by Mr. Moore before the Geological Society of London, 

 in which he strenuously adheres to his view of the Liassic 

 character of the beds in question, and maintains his argiiment 

 with all the force which a long and intimate acquaintance with 

 their contained organisms enables him to bring to bear upon the 

 subject. He takes the whole line of country from Frome, in 

 Somersetshire, to Sutton, Southerndown, &c., in Glamorgan. 

 He first alludes to the Mendip up-Kft, its basaltic dykes, &c., 

 and describes the physical changes produced. He then points 

 out the normal condition of the secondary deposits south of the 

 Mendips, and shews that everything within the coal-basin is 

 either in a great degree uncomformable or abnormal. He takes 

 the Camel Section as the typical one, which he divides as 

 follows: — 1. Keuper 



2. Rhsetic 



3. Insect and Crustacea beds 



4. Ostrea bed 



6. Am. planorbis bed ; 



