162 PKor. o. T. JONES o]sr [vol. Ixxvii, 



characters from those of the Haverford Stage, and towards the 

 top early variants of Plecfamhonltes transversalis make their 

 appearance. That species itself has not, hitherto, been proved to 

 occur in the Yalentian. 



The foregoing summar\^ of the faunal characters of the Millin 

 Stage might be applied almost word for word to the Camregan 

 Group of Girvan. Among other forms which occur in the 

 Camregan Beds are Harrandella iindata, var. 'penkiJlensis Reed 

 (which is identical with that of the basal beds of the Millin Stage). 

 Catazyga liasivelli, Spirifer radiatus, Cyrtia exporrecta, ' Stro- 

 'phomena arenacea^ and the abundant species of Plectamhonites 

 which Dr. F. R. C. Reed has also erroneously referred to P. trans- 

 versalis. Many of the forms of PJiacojjs are identical with those 

 of the Millin stage, while in both districts there are examples 

 intermediate between them and Ph. stokesi. 



There is a further remarkable similarity in the lithological 

 characters of the beds ; the mudstones in both districts are 

 greenish, and the fossils, where weathered, are preserved as casts 

 coated with a pale-yellow limonitic material. The sandy beds are 

 greenish with a bluish interior, while the basal beds in both dis- 

 tricts are pebbly. There is, however, one striking difference : in 

 the Camregan Group Peiitamerus ohlongus is an abundant fossil ; 

 but it has not been found so far in any part of the Millin 

 Group. The distribution of this species is peculiar, and appears to 

 be related to the conditions of deposition : it is abundant, for 

 example, in the Caradoc and Eosemarket areas ; while it is gener- 

 ally rare, or even absent, in the South-West of England and in 

 the Marloes-Wooltack area. It is interesting to note, however, 

 that it occurs in the Llandovery district associated with the most 

 characteristic elements of the Millin fauna. 



In the higher or Canaston subdivision of the Millin Stage 

 Barrandella glohosa is an abundant species, and is a characteristic 

 index of the group. It is accompanied in some localities by a 

 large variet3^ In the highest beds exposed in Pembrokeshire 

 jB. glohosa is associated with numerous examples of a species of 

 PalcBocyclus. It is doubtful whether the typical B. glohosa 

 occurs in the Girvan district ; it might be expected to occur in 

 the Penkill Group, which is, however, largel}^ of graptolitic facies 

 except at a few horizons. It is of considerable interest to find 

 that a small Palceocyclus which is indistinguishable from the 

 Pembrokeshire specimens occurs abundantly at Blackwood Head 

 Burn in company with Pentamerus ohlongus. This horizon is 

 in the Blackwood subdivision of the Bargany Group, which lies 

 a considerable distance above the zone of Gyrtograptus grayce, or, 

 in other words, near the junction of the Lower and Upper Gala. 

 The PalcBocyclus Beds probably fall, therefore, within the Upper 

 Gala, Avhen referred to the graptolitic scale. 



The Haverford Stage as a whole may, therefore, be compared 

 with the two main fossiliferous groups of the Newlands Stage 

 •of Girvan; while the two subdivisions of the Millin Stage 



