part 2] THE TALENTIA^^ SERIES. 161 



works Mudstones may be regarded as substantially correct. It is 

 probable, however, that the upper part of the Haverford Stage 

 extends beyond the uj)per limit of the Woodland Beds, and may 

 thus be equivalent to the Glen Shalloch graptolite-shales. The 

 Mulloch-Hill Beds probably correspond to the lower part of the 

 Haverford Stage, which is relatively barren of fossils. 



The Millin Stage.— The base of the Millin Stage in the 

 Haverfordwest district has been taken at the bottom of a group 

 of greenish, occasionally purple, rubbly unfossiliferous mudstones, 

 which pass down conformably into the Gasworks Sandstone. On 

 physical grounds this choice has little to recommend it ; but, the 

 boundary between the sandstone and mudstones being easily trace- 

 able, it facilitated the mapping. The mudstones are succeeded 

 by a group of sand}^ pebbly beds which contain the characteristic 

 fossils of the Millin Stage, and probably represent the true basal 

 beds of that stage. In view of the remarkable contrast between 

 the Millin fauna and that of the Haverford Stage, it is not un- 

 likely that the pebbly beds mark an important change of phj^sical 

 conditions during the deposition of the sediments, if not a strati- 

 graphical break. A change of j^hysical conditions is, in fact, 

 foreshadowed by the greenish and purplish rubbly mudstones 

 which succeed the Gasworks Sandstone, and were formed under 

 conditions unfavourable to organic life. 



At the base of the Millin Stage several species appear for the 

 first time in the ascending sequence, which either range up into 

 the Wenlock, or are represented in that formation by closely-allied 

 forms. Many of these are spire-bearing brachiopods which are 

 markedly characteristic of the higher Valentian and Wenlock 

 rocks : thus ^pirifer radlatus and Cyrfia exporrecta both range 

 into the Wenlock; while the abundant Catazyga liaswelli is closely 

 allied to the Wenlock C. pentlandica. 



Many of the Strophomenidye of this stage, such as Schucliertella 

 appJanata^ are common Wenlock forms ; while even the stage of 

 development indicated by the varieties of Lepfcena rhomhoidalis 

 is more nearly like that of the Wenlock than of the Haverford 

 types. 



The group of globose Pentaraerids represented by JSarrandeUa 

 glohosa and its varieties is unknown below this horizon, but they 

 range upwards through the Yalentian. and even in some localities 

 (Marloes and Wooltack) possibly into the base of the Wenlock 

 Series. Again, Afrypa reticularis appears in abundance at this 

 horizon, but in the Haverfordwest district, at any rate, has not 

 been found below : it is, of course, a well-known Wenlock species. 

 The facies of the fauna is indeed so thoroughly reminiscent of 

 the Wenlock Shale that, if it were not for the ]:)resence of certain 

 Pentamerids and of species of I^hc/cops which are not known to 

 occur in the Wenlock, the Millin rocks might easily have been 

 referred to that formation. 



The stage is characterized b}?^ abundant forms of JPlectamhonifes, 

 which are readih^ distinguishable by their size, shape, and internal 



