4gg J. E. MAEE AND T. EOBEETS ON THE 



looical character were being laid down, as the Lower Llandovery 

 he*ds closely resemble the Slade beds lithologically. 



8. Loiuer Llandoverij ^gcZs.— These beds are, as explained above, 

 apparently faulted against the lower beds in the immediate neigh- 

 bourhood "of Haverfordwest. They are usually very highly inclined, 

 and stretch to the south of the town for nearly two miles. The 

 well-known section at the Gas-works shows the general character of 

 the rocks, which consist of gritty green shales, with bands of grit, 

 and weathered calcareous bands crowded with fossils. As the 

 organisms of this deposit are preserved in many museums, it is un- 

 necessary to give a full list. Niclulites favus, Petraia suhduplicata 

 var. crenulata, Tentaculites anglicus, and brachiopods, lamellibranchs, 

 and gasteropods are all abundant. Amongst the fossils hitherto 

 unrecorded from these beds are Phacops elegans, Boeck and Sars 

 r = eIJiptifrons, Esm.), and Deiplion Forhesi, Barr. A fine specimen 

 of the latter was presented to the Woodwardian Museum by Mr. H. 

 T. WiUs. 



§ 3. Com]Darison with the Deposits of other Areas. 



The resemblance of many of our stages to those of other areas, 

 whether we take into account their lithological or palseontological 

 characters, is so striking, that it cannot be a mere coincidence, 

 especially as this resemblance does not occur in isolated stages, but 

 in the consecutive stages of some of the series. We propose, there- 

 fore, to point out briefly some of these similarities, as they afford 

 assistance in attempting the correlation of deposits of different 

 areas. 



i. Lhigula-Flags. — These beds appear, from the occurrence of 

 Olenus spinulosus, to represent the Lower Dolgelly beds of the 

 Lingula-Elags of North "Wales, which are correlated by Prof. 

 Brogger (Sil. Et. 2 and 3, p. 144) with his "Paraholina-spinulosa 

 niveau " (2 b) in the Christiania district, where that fossil is likewise 

 associated with Agnostics socialis. 



It is desirable, however, that additional species should be obtained ; 

 for whilst the fossils already procured leave no doubt as to the 

 Lingula-Elag age of the rocks containing them, it is perhaps 

 dangerous to attempt to assert positively to what portion of the 

 Lingula-Elag series they belong, without further evidence. 



ii. Didymogra/ptus-Shales. — The " tuning-fork " graptolites of 

 these beds are characteristic of Dr. Hicks's Llanvirn beds in the St.- 

 David's district, as elsewhere. As the horizon is so well known in 

 many places, and coutains this particular type of graptolite, it is 

 needless to give a list of deposits of the same age in other areas. 



iii. Llandeilo Limestone. — The remark just made applies in this 

 case also. The position of the Asaplius-tyrannus beds is well estab- 

 lished in South Wales. At the same time it is possible that the 

 beds included in the Llandeilo limestone of other regions are partly 

 represented by the lower beds of the succeeding division of the 

 Haverfordwest district ; for whereas Ogygia Buchii has not been 

 discovered by us in the limestone, and is apparently not recorded 



