Hughes — Geology of the Lake District. 355 



Beck we have an ascending series, and just above the limestone find 

 shales in which Strophomena alternata is the characteristic fossil ; and 

 much higher up, on the south-west side of Eawthay Bridge, shales 

 in which Trinudeus is abundant. 



Limestones always form a convenient dividing band, both from 

 their pointing to some physical change, and from their marked 

 lithological character. Therefore, although B.a. passes down into 

 B.6., we may take an arbitrary line for the base of B.a., and we 

 shall find that a change has set in somewhere thereabouts. 



In B.a. I have found — 



0. calUgramma — large close ribbed var. 



0. sp. 



Strophomena depressa. \ Abundant in 

 S. alternata. > the 



/S. sp. ; lower part. 



Orthoceras, etc., etc. 



Petraia subduplicata, var. crenulata. 

 Encrinites. 



Phacops apiculatus ? \ n\,- a • 

 Phacops, sp. {pbtusi- \ ^^^l^ ^" 

 caudatus ?) I . 



Trinucleus concentricus. / "" " ' 

 Orthis biforata. 



A.c. 4. This bed is seldom exposed. Probaby it does not every- 

 where exist as a conglomerate, and, moreover, in the other parts 

 of this district which I have had an opportunity of examining, I 

 have never found the upper group near the lower, except where 

 I have plenty of independent evidence of its being brought on by a 

 fault. It is, however, well seen in a few places in the Crummack 

 Valley, where it is a very coarse irregular conglomerate, made iip of 

 rolled and angular fragments, which appear to be derived from the 

 grits and fine conglomerates of the green slates ; from the Coniston 

 Limestone series — some pieces are very like a bed seen in B.a. 

 close by ; — bits of quartz and slates of various texture, etc. The 

 greatest thickness I could measure was about ten feet. The only 

 fossils I found were Favosites alveolaris? F. fibrosa. It may be 

 that the breccia-like limestone above the Coniston Limestone at 

 Crag Hill is the equivalent of this conglomerate. I have nowhere 

 seen a limestone of that character in the Coniston Limestone, where 

 it has been covered by beds undoubtedly belonging to the lower 

 group B. ; also, the only fossils I found in it were the same corals 

 1 found in the conglomerate ; but this is a point to be worked out. 



A.c. 3. Slates very uniform in character throughout. Generally 

 a soft raudstone splitting by cleavage and joints into small rhom- 

 boidal pieces. Faint lines often indicate the bedding. I have not 

 as yet found any fossils in these beds. The thickness is probably 

 several hundred feet. They pass up through a roughly cleaved 

 sandy slate into — 



A.c. 2. Tough grits, or greywacke,^ with subordinate beds of 

 flags. These have as yet yielded no fossils. They are about one 

 thousand feet thick, and always, in this district, succeed the slates 

 (A.c. 3) with a very uniform character and thickness. 



A.c. 1. Flags with subordiiiate thin beds of grit. These are the 



* The word "greywaclce" as defined by Mr. Forbes (p. 229, sup. foot-note) would 

 be a very useful term in this country. We want a name for the tough Silurian rocks 

 which seem to be something between a grit, or sandstone and quartzite. — -See Geol. 

 Mag., Vol. III. p. 206, foot-note. 



