part 2] THE VALENTIAW SERIES. 157 



From the Shalloch Forge localit}^ where the same shales are ex- 

 posed, Diplograftas modestus was also obtained, but in association, 

 Among others, with Monogrccptus cyphus. Most of the forms 

 which have been referred to J£ ci/plius indicate a horizon not 

 higher than the lower j^art of the M.-triangulatus Zone. A search 

 made by me at this locality yielded the following forms : — Mono- 

 graptus revolutas c. and var. austerus, 11. sandersoni, M. sp. 

 (which is almost certainly M. atavus), Mesograptiis modestus 

 var. diminutus, and an extraordinary abundance of Glyptograpius 

 tamariscus. The general association of these graptolites, especially 

 the occurrence of M. saiidersoni and the absence of JSLonograpii 

 of the triangidatus or comiiiuriis types, probably indicates the 

 M.-cgplius Zone in its restricted sense. The horizon is, therefore, 

 fixed within narrow limits, since that zone is in most areas of small 

 thickness. 



According to Lapworth, the highly-fossiliferous Woodland 

 Limestone and Shale occur not far beneath the graptolitic shales. 

 As noted above, the lowest graptolitic horizon exposed in the New- 

 lands region is the lowest part of the JM.-tvicuigulatus Zone, and 

 therefore only just above the Shalloch Forge horizon ; even in 

 districts where the Birkhill sequence is of considerable thickness, 

 "the difference in stratigraphical level between these horizons does 

 not amount to more than a few feet. It is probable that, as 

 Lapworth suggested, the Woodland Beds do not immediately 

 underlie the graptolitic sliales, but are equivalent to a thin calca- 

 Teous seam in Penwhapple Glen, which is also associated with 

 graptolitic shales. An examination of numerous specimens from 

 this locality, preserv^ed in the collection of the Geological Survey 

 of Scotland, allows the horizon of these shales to be fixed with con- 

 siderable precision. The most important forms identified were : — 

 Mo nog rapt us atavus v.c, M. sp. different from ataviis, but re- 

 calling J\L aciiiaces, Dimorphograptus confertus c, D. cf. longis- 

 ■simus v.c, D. cf. erectiis, Climacograptus toernqnisti, and some 

 others. JSLonogrcptus revolutus and Mesograptus modestus var. 

 dlniinutus were collected by Mr. Macconochie and myself during 

 •our visit. The association of abundance of Monograptus atavus 

 with various Dimorphograptidse and Climacograptus toernquisti 

 indicates a horizon near the top of the M.-atavus Zone of Central 

 Wales; but the presence of a second species of Monograptus 

 points to a slightly higher level, the difference being, however, 

 only a few feet. 



The Woodland Beds apparently occupy a position immediately 

 below this horizon, and they correspond, therefore, to the interval 

 represented by the Monograptus-atainis Zone, and possiblv a part 

 of the succeeding M.-acinaces Zone. 



The Dailly Stage: the Camregan Limestone Group. 

 — The reasons for including this group with the Upper Yalentian 

 have already been stated ; the position of the group on the grapto- 

 litic scale is clearly defined by the zone of Mastrites ma.viinus 

 within it. An approximate lower limit is indicated by the fact that 



n2 



