Vol. 69.] PALEOZOIC ROCKS OF THE CAUTLEY DISTRICT. 3 



The most abundant fossil here, as elsewhere in these beds of the 

 district, is the Galymene. The form, is that recorded by Salter as 

 C. senaria Conrad in the Sleddale Beds of the Lake District. Mr. F. 

 11. C. Reed has, however, shown that the form is not Conrad's 

 species, and has given it a new name, C. planimarginata. 1 From 

 its abundance, the beds will be referred to as the Calymene 

 Beds. I have hitherto found no form of this or any other species 

 of the genus in higher Ordovician deposits of the Cautley neighbour- 

 hood ; it is, therefore, a particularly characteristic fossil. 



Above the highest exposure with Oalymene a considerable thick- 

 ness of similar strata occurs, which has yielded, so far, neither the 

 Galymene nor any characteristic fossil of the succeeding beds; and 

 in Backside Beck, therefore, one cannot, within a limit of 100 feet 

 or more, draw a line of demarcation between the Calymene Beds 

 and the succeeding strata, to be next described. In other words, it 

 is not at present possible to indicate here the exact line of sepa- 

 ration between the Caradocian and the Ashgillian strata. The first 

 characteristic assemblage of Ashgillian forms has been found about 

 300 yards higher up the stream than the point yielding the last 

 Galymene; as, however, the strike is, for some distance, nearly 

 parallel to the stream, and a considerable stretch is occupied by a 

 f el site sill, the thickness is not very great. The evidence, on the 

 whole, is in favour of the beds immediately above the ruined foot- 

 bridge belonging to the lowest Ashgillian group. Impure limestones 

 and calcareous shales immediately above the bridge have yielded 

 Turrilepas ; and a little higher up, just below the felsite sill, a 

 specimen of Strophomena corrugatella occurred. Lithologically, the 

 beds suggest rather Ashgillian than Caradocian deposits, but one 

 cannot lay much stress upon this point. 



Where the northern wall of a pasture west of the beck comes down 

 to the stream, beds occur with Remopleurides and Phacops robertsi, 

 striking generally along the stream to the junction of Watley Gill, 

 where they form a cliff on the right bank of Backside Beck. These 

 beds are lithologically similar, on the whole, to those of the Caly- 

 mene Group. Like the latter, they consist of shales and impure 

 limestones. The shales, however, are generally lighter in colour, 

 grey rather than black, and have an unctuous feel ; but individual 

 bands are quite similar to some of the Calymene Beds. 



Similar as are the lithological characters of the two groups, their 

 faunas are markedly different, and the fossils of the upper group 

 have a distinctly Ashgillian facies. Remopleurides and Phacops 

 robertsi occur throughout, the latter being most abundant near the 

 base. I shall speak of these beds as the Phacops- robertsi 

 Beds. 



Fossils occur in the limestones as well as in the shales, and, 

 although in the former they are usually fragmentary, the details of 

 structure and ornament are beautifully preserved. The following 

 is a list of forms found in the Phacops-robertsi Beds of the beck : — 



1 See ' Lower Pakeozoic Trilobites of Grirvan ' pt. 3, Monogr. Palseont. Soc. 

 (1906) p. 137. 



B2 



