SILTJKIAN OF THE LAKE-DISTRICT. 



879 



These fossils were found in every case in beds included between 

 undoubted Graptolitic Mudstones. The position of the Skelgill fossils 

 is indicated by the letters annexed to them, which refer to the zones in 

 the section given. The fossils of Spengill and Torver Beck came from 

 flaggy beds with calcareous concretions, passing in places into im- 

 pure limestone, occurring in each case near the top of the Graptolitic 

 Mudstones. Lastly, the Peltocaris from Long Sleddale was found in 

 the midst of the Graptolitic bands. 



On looking at the list, more especially that of the Crustacea, we 

 are at once struck with the Silurian facies of the genera. Acidaspis, 

 Proetus, Harpes, and Encrinurus are genera never occurring as the 

 characteristic Trilobites of even the highest beds of the Cambrian 

 series ; and I can find no instance where they occur associated in 

 abundance in that series, as is the case in the Graptolitic Mudstones. 

 On the other hand, such Trilobites as Trinueleus, Lichas, Cybele, 

 Asaphus, and the large species of Phacops of the subgenus Chasmops, 

 so typical of the Bala beds, are totally absent from this list. The 

 Phacopes present, probably referable to two species, both belong to 

 the subgenus Phacops proper, which I cannot find recorded from 

 Cambrian rocks, but which is abundant in Silurian. When we 

 examine the species, the same conclusion is borne out. Of the Ac- 

 tinozoa, the Favosites is one which occurs in the Coniston Elags. Of 

 the Crustacea, Discinocaris has only been found in the Moffat Shales, 

 and occurring in the mudstones, which have been a subject of much 

 dispute, together with the Graptolites, must be considered along 

 with them. One species of Acidaspis seems absolutely identical 

 with a species found in the May-Hill beds of Penlan, Llandovery. 

 The Harpes I have not been able to determine with certainty. It 

 is possible there may be two species here. Some specimens much 

 resemble one of the Bohemian species of Etage E ; and, indeed, all 

 the fossils form a very similar group to that found in this Bohemian 

 division. Cheiruras bimucronatus, although found in the Bala beds, 

 is much more abundant in the Wenlock Limestone. The Phacopes 

 have been already alluded to ; one much resembles Phacops StoJcesii, 

 so characteristic of Wenlock rocks. Encrinurus variolaris is a fossil 

 confined exclusively to Silurian rocks. The Mollusca do not yield 

 much evidence, being small and badly preserved ; the only species I 

 have determined is Leptcena quinquecostata, which is exceedingly 

 abundant at Spengill. It is mentioned in Davidson's monograph 

 as ranging from Lower Bala to Upper May-Hill beds. Thus the 

 fossils indicate the Graptolitic Mudstones to have been deposited 

 during the Silurian period. It would be impossible at present to 

 correlate them with their equivalents in Wales ; but the beds above 

 them have been identified, by Mr. Aveline, with the Tarannon 

 shales (Geol. Mag. decade ii. vol. iii. p. 376), whilst the basement- 

 bed presents many affinities with the Lower May-Hill beds of Wales. 

 In this case the Graptolitic Mudstones would be either upper May- 

 Hill beds, lower part of the Tarannon shales, or intermediate beds ; 

 and the fossils in some degree bear out this view. Of the Graptolites 

 I need not treat, but will consider only the evidence derived from 



he more highly organized fossils. 



