﻿Vol. 6 1.] ANNIVERSARY ADDRESS OP THE PRESIDENT. lxXXUl 



Dr. Hicks that certain beds in South Wales, which he grouped as 

 Lower Arenig, were contemporaneous with the Upper Tremadoc 

 Slates of North Wales. This is a matter which requires clearing up. 



kj2. The Llandeilian Series. — In South Wales the plane of 

 demarcation between Skiddavian and Llandeilian rocks is well 

 shown, and separates the beds with Didymograptus bijtdus. which 

 belong to the top of the Skiddavian, frorn the basal Llandeilian 

 Beds with Didymograptus Murchisoni. 



In a paper in the ' Popular Science Eeview ,l Dr. Hicks proposed 

 grouping the uppermost Skiddavian and lower Llandeilian Beds 

 as a new series, to which he gave the name of ' Llanvirn/ The 

 fauna of this series is strongly developed in Central and North - 

 Western Europe, although it is doubtful how far that fauna is of 

 Llandeilian age. It may ultimately be found expedient to restrict 

 the Skiddavian and Llandeilian groups, and to separate a Llan- 

 virnian Series ; but at present the divisions which were originally 

 defined by Murchison and Sedgwick appear sufficient. 



Murchison's Llandeilo division is perfectly-well defined, and in 

 the typical area contains three faunas. We are enabled, therefore,, 

 to classify the Llandeilian as follows : — 



{Upper beds with Nemagraptus ( Coenograptus) gracilis. 

 Middle beds with Asapkus tyrannns. 

 Lower beds with Bidymograptus Murchisoni. 



In the St. David's region Hicks discovered a fair number of fossils 

 other than graptolites in the upper and lower beds, which, with 

 the faunas described by Prof. Lapworth in the Girvan area, have 

 given us some knowledge of the nature of the Llandeilian faunas 

 preserved in the non-graptolitic deposits. 



3. The Caradocian Series. — 'The term 'Bala' has been 

 used in so many senses that it will be well in future to retain 

 it for the lithological divisions in the Bala district. Sedgwick 

 ultimately divided his Bala Beds into three groups, of which the 

 lowest was the equivalent of the Llandeilo Beds, while the upper- 

 most included strata which do not appear to be represented in the 

 Caradoc area. The term ' Caradoc,' on the contrary, was given by 

 ^Furchison to a group of rocks which are clearly separated from 

 the Llandeilo Beds beneath, and, as above, stated, do not include 



1 ' The Classification of the Eozoic & Lower Pakeozoic Eocks of the British 

 Isles' Pop. Sci. Kev. n. s. vol. v (1881) pp. 302-303. 



