Rev. J. Clifton Ward — Geology of the Lake District. 123 



sandy series of beds so largely developed in Grasmoor and Whiteside, 

 either thin eastwards or have their place taken by less sandy and 

 more slaty deposits in this direction ; this, combined with excessive 

 faulting, and the difficulty in tracing the faults, owing to contortion 

 and cleavage, makes it exceedingly hard to draw the actual 

 boundaries of these groups in many places. 



Points of JPalceontoIogical Evidence. — In assigning the whole thick- 

 ness of the Skiddaw Slates to the Lower Llandeilo, and that mainly 

 on the strength of the Graptolite fauna, Axiom (3) is distinctly 

 transgressed in both its clauses, for the Graptolite family cannot be 

 taken as a characteristic assemblage of life in general, and the forma- 

 tion above (the Volcanic Series) is unfossiliferous, while nothing is 

 known of that below. Still, the group of Graptolites being such as 

 is known to be characteristic of rocks of Lower Llandeilo age else- 

 where, is evidence of considerable value, though not to be too 

 exclusively relied on ; but when the palaeontologist says further that 

 the whole of this Skiddaw Slate Series must be L. Llandeilo because 

 Graptolites do occur throughout, or nearly so, I for one am inclined 

 to demur. Could a L. Llandeilo assemblage of fossils be shown to 

 prevail throughout the series, the case would be different. But it so 

 happens that among the Trilobites there are several Tremadoc forms 

 — see notes by Mr. Etheridge, F.K.S., at the end of the Survey 

 Memoir — and with them a species of Cybele hitherto only represented 

 by species not occurring below the Caradoc rocks. Certainly the 

 scanty evidence to be derived from the group of Trilobites is con- 

 flicting, and besides Trilobites and Graptolites, we have but a few 

 doubtful plant-remains, carapaces of Phyllopod Crustacea, a Lingula 

 (brevis), and doubtful Discina, and worm-tracks. Under these 

 circumstances no wonder that the Graptolites are referred to as the 

 most important. Hence we have the evidence of this group in 

 favour of the L. Llandeilo age of the Skiddaw Slates, and the 

 evidence of at least part of the Trilobite fauna in favour of the 

 Tremadoc age of portions of the series. The question arises, are we 

 justified in saying that such and such beds below a certain horizon 

 cannot be of Tremadoc age because beds believed to be of that age 

 in Wales do not contain Graptolites ? A thin grit in Wales separates 

 black slates above, containing Graptolites, from black slates below 

 not containing them ; the upper are called Arenig, the Lower 

 Tremadoc : are we to assert from this that, such being the case in 

 Wales, so far as our experience goes, no black slates, whatever their 

 physical position, which contain Graptolites, can be of Tremadoc 

 age ? Surely not. In Cumbria we have a grit, similar to the 

 Arenig grit of Wales, with black slates above containing Arenig 

 Graptolites, but in this case the black slates below also contain 

 them ; therefore the palaeontologist says these cannot be Tremadocs, 

 and yet there may be but 50 feet or less of grit separating the two 

 series. For my own part, while ready enough to accept the evidence 

 of palaeontology when it is presented in the form of life assemblages, 

 I do decline to pin my faith as to the succession and equivalence 

 of rock-groups to the evidence afforded by the finding of a few 



