520 Geological Society. 



to run persistently across the district, with the exception of the 

 zone of Rastrites maximus, which has only been discovered in the 

 Sedbergh area. The thicknesses, lithological characters, and fossil 

 contents of these zones were considered, and comparisons made 

 between these beds and the corresponding deposits of other areas. 

 The whole group attains a thickness of from 250 to 400 feet, of 

 which the Skelgill beds usually make up about one quarter. 



The authors correlate the Graptolite-zones with those of the 

 Birkhill and Gala groups of Professor Lapworth as follows : — 

 Lake District. South of Scotland. 



Zone of Monograptus crispus = Zone of M. cxiguus. 



„ turriculatus Not separated. 



,, Rastrites maximus = Zone of R. maximus. 



Monograptus spinous 1 Monograptus spinigerus. 



Monograptus Chnganib&na J J * r * 



Not represented ? „ Pctalograptus cometa. 



Zone of Monograptus convolutus 1 



„ argenteus L = Zone of M. gregarius. 



„ fimbriatus J 



„ Dhnorphograptus confertus = „ Diplograptus vesiculosus. 



„ Diplograptus acuminatus = „ D. acuminatus. 



The zones of M. convolutus, M. argenteus, and M. fimbriatus con- 

 tain abundance of M. gregarius, and the zone of Dimorphograptus 

 confertus also contains Diplograptus vesiculosus in considerable 

 numbers. 



The beds were also compared with the corresponding beds in 

 Sweden, Bohemia, Bavaria, &c, and the fossils other than Grapto- 

 lites were shown to occur elsewhere in strata of Llandovery-Tarannon 

 age, from which it was concluded that the Stockdale Shales occupy 

 that horizon. 



A fault occurs everywhere between the Middle and Lower Skelgill 

 Beds, except perhaps in the Sedbergh district ; but it does not seem 

 to cut out a great thickness of rock, and the authors gave reasons 

 for supposing that it was produced by one set of beds sliding over 

 the other along a plane of stratification. 



The beds are found to thicken out in an easterly direction, and 

 the possibility of the existence of land in that direction was suggested. 



The authors directed attention to the importance of the Graptoli- 

 toidea as a means of advancing the comparative study of the strati- 

 fied deposits of Lower Palaeozoic age. 



A description was given of the following new species and varieties : — 

 Phacops elegans, Boeck tfe Sars, var. glaber, Cheirurus bimucronatus, 

 Murch., var. acanthodes, Cheirurus moroides, Acidaspis erinaceus, 

 Harpes judex, H. angustus, Ampyx aloniemis, Proetus brachypygus, 

 and Atrypa flexuosa. 



2. " On the Eruptive Bocks in the Neighbourhood of Sarn, Caer- 

 narvonshire." By Alfred Harker, Esq., M.A., F.G.S. 



The rocks in question occupy an area about 5| miles long from 

 north to south and 2^ miles broad near the south-western extremity 

 of Caernarvonshire. They were described by the author under the 

 following heads : — 



