Vol. 62.] TAEANNON SEEIES OF TAEANNON. 699 



Andrew, and Mr. G. A. Shakespear for help in collecting in the 

 field ; and to Dr. Herbert Lapworth for assistance in the identi- 

 fication of some of the more difficult graptolite-forms. Especially 

 do I wish to express my gratitude to Prof. Charles Lapworth, who 

 has assisted me with advice and helpful criticism. 



EXPLANATION OF PLATES XLVII & XLYIII. 



Plate XLVII. 



Geological sketch-map of the Tarannon country, on the scale of 4566 feet to 



the inch. 



Plate XLVIII. 



Fig. 1. Horizontal section along the Afon Iaen, on the scale of 3 inches to 

 the mile. 

 2. Generalized section from Dolgadfan to Talerddig, across Newydd 

 Fynyddog, on the scale of 3 inches to the mile. 



Discussion. 



The President congratulated the Authoress on the lucid and 

 interesting way in which she had presented her subject to the 

 Society. As an old member of the Geological Survey, he would 

 like to express the satisfaction with which he observed that the 

 subdivision of the Tarannon Shales, first distinguished and mapped 

 on merely-lithological grounds by his friends and colleagues, Jukes 

 and Aveline, had been sustained on palreontological evidence by 

 subsequent observers, and that the original tract of Tarannon, at 

 last so thoroughly worked out, zone by zone, by the Authoress, had 

 been shown by her to contain so full and typical a development of 

 this important group in the Upper Silurian Series of formations. 



Dr. Maee said he felt that he might have been mistaken in 

 referring the Cerrig-y-Druidion beds, of which the Authoress had 

 spoken, to the Birkhills; they might well be of Tarannon age. 

 He thought that the Rastrites-maximus beds of the Sedbergh district 

 were more closely linked to the Skelgill than to the Browgill Beds. 

 In conclusion, he expressed his high appreciation of the paper. 



Mr. Hopeinson said that he had listened to the paper with very 

 great interest, and he was pleased to find the graptolites playing 

 the leading part in so important a communication on the Silurian 

 rocks of Wales. They were proving, as it was anticipated that 

 they would, long before the species had been so well worked out by 

 Miss Elles and the Authoress, invaluable in correlating the rocks 

 of distant areas ; and he thought that if the Authoress were to 

 extend her researches into Bohemia, she would find the same 

 succession of species in the rocks from which Barrande obtained the 

 graptolites described by him many years ago. 



Prof. Watts, with the President's permission, read the following 

 contribution to the Discussion sent by Dr. Heebeet Lapwoeth : — 



' I very much regret that I am not able to be present, but I have been 

 through the manuscript and noted the main points, and was particularly 



