694 MISS E. M. K. WOOD ON THE [Nov. I906, 



The lowest graptolitiferous band in the Brynmair Beds (zone 

 of Monograptus turriculatus) is that containing Rastrites maximus. 

 This has only been detected with certainty at one locality, and has 

 there yielded nine species. Of this total six occur in the zone of 

 R. maximus in the South of Scotland and six in the Lower Gala 

 Beds. Considering now this fauna in the Tarannon district, it is 

 found that only R. maximus itself is restricted to this band, the 

 remaining eight species occurring in the succeeding beds of the 

 Brynmair Group. Only one species — Monograptus Halli — has at 

 present been detected in the underlying ' M.-Sedgwickii' Beds, 

 although M. runcinatus and M. jaculum, which occur in both the 

 M -Sedgwickii and M -turriculatus Beds, will probably be detected 

 in the intervening R.-maximus band. If we include in this band 

 the species collected from the bed in the upper part of the Twymyn 

 Yalley (p. 688), at the base of the Brynmair Group, the abrupt 

 change in fauna is less conspicuous; but even in this case the 

 palseontological break between the ' SedgivicJcii '- and ' maximus '- 

 beds is far more marked than it is between the ' maximus '-band 

 and the rest of the Brynmair Group. At any rate, it is clear that 

 in the Tarannon district the band with Rastrites maximus must fall 

 into line with the remainder of the Brynmair Beds, and is hardly 

 worthy of differentiation as a distinct band. 



The fauna of the Brynmair Group, as a whole, varies considerably 

 between its lowest and its highest limits, and additional work might 

 lead to further zoning, but our knowledge is at present insufficient. 

 Monograptus turriculatus occurs throughout the group, but is most 

 abundant in the lower beds, where it is generally associated with 

 M. runcinatus, M. Bechi, and Rastrites Linnmi. The higher beds 

 are apparently characterized by the presence of Monograptus proteus 

 and a form which is best compared with M. densus, Perner ; while 

 M . exiguus does not make its appearance until the higher beds. Of 

 the total of 27 species found in the Brynmair Beds, 14 occur in the 

 Lower Gala of the South of Scotland, and the comparison is again 

 still closer if we include new species. There can be no doubt, 

 therefore, that the Brynmair Group corresponds to part, at any rate, 

 of the Lower Gala Beds and the zone of Rastrites maximus. 



As regards the Gelli Group, an examination of the lists shows 

 that out of its eleven species, six occur in the Lower Gala Beds, 

 and four in the Upper Gala. Thus, these beds have on the whole 

 affinities with the Lower Gala, rather than with the Upper, 

 especially as the characteristic graptolite of the Gelli Group — 

 namely, Monograptus crispus — is confined to the Lower Gala Beds. 

 Hitherto M. exiguus has been regarded as the zone-fossil of this 

 horizon, but in the Tarannon district this species is not so restricted 

 in range as M. crispus, and this latter has therefore been selected as 

 the local zone-fossil. 



A reference merely to the published lists gives but little guidance 

 to the true zonal position occupied by the Talerddig Group. As 

 a matter of fact, however, the species found in these beds are almost 

 identical with those from the Grieston Beds of the South of Scotland, 



