696 MISS E. M. B. WOOD ON THE [NOV. I906,. 



The assemblage of species found in the lowest band of the ' con- 

 volutus '-zone agrees well with that from the Calcareous-jSodule 

 Beds of the Gigrin Mudstones ; while that from the higher band 

 may best be compared with Dr. Herbert Lapworth's succeeding 

 zone of Monograptus convolutus. 



The Twymyn Beds find their nearest palaeontological equivalents 

 in his Caban Group ; but the lithological characters of the two 

 groups are so different that a close comparison is impossible. 



As to the Rhayader Pale Shales, Dr. Herbert Lap worth has 

 shown conclusively that eighteen out of the nineteen species detected 

 in these beds are identical with those from the Lower Gala Group 

 and Rastrites-maximus zone combined of the South of Scotland. 

 We can therefore have no difficulty in paralleling his Rhayader 

 Pale Shales with the lower part, at any rate, of the Tarannon Group. 

 A reference to the lists in Table II (facing p. 692) will show that the 

 graptolites collected by him from the lower part of the Pale Shales, 

 namely in the western area, are very similar to those occurring in 

 the Brynmair Shales ; while those obtained by him from the upper 

 part, in the eastern area, agree almost precisely with those from the 

 lower part of the Gelli Beds. 



When we compare the graptolitic species found in the so-called 

 'Tarannon Shales ' of Conway, as cited in the list in Table I (facing 

 p. 692), which has lately been revised by Miss Elles and myself in 

 the light of further knowledge, we find that it is possible to draw 

 a close parallel between them and the Brynmair Shales. At 

 Conway Monograptus crispus has not been recognized hitherto with 

 certainty ; and although M. exiguus is a fairly-common species there, 

 it is subordinate in importance to M. turriculatus, and therefore the 

 highest part of the Gelli Shales is certainly not represented in the 

 section studied by us. The ' Tarannon Shales ' at Conway (which 

 include the band separated off as the zone of Rast rites maximus) cor- 

 respond apparently to only the lower fourth of our Tarannon Series. 



An examination of the fossil lists of the Skelgill, Browgill, and 

 Brathay Flags of the Lake District reveals a remarkable agreement 

 between their zones and those of the Tarannon district. It is 

 interesting to note in the Browgill Beds the occurrence of the same 

 two local zones of Monograptus turriculatus and M. crispus, especially 

 as hitherto the separation of these two zones in the Lake District has 

 not been corroborated elsewhere. 



The only graptolitic beds on the Continent with which we need 

 parallel the Tarannon strata are the Rastrites-Skifter and the Cyrto- 

 graptus-Skiffer of Scania. The Rastri tes-Skiffer have been divided 

 by Prof. Tornquist into six zones ; and the assemblage of species of 

 each of these agrees closely with that of the five zones of our 

 Llandovery Series, and with the lowest of our Tarannon Series (zone 

 of Monograptus turriculatus), although the graptolite-species selected 

 for the local zone-fossil is not the same in every case. 



Prof. Tornquist's zone of Monograptus runcinatus appears to 



