Geological Society. 1 49 



A paper entitled " Notices on the Geology of the North-west of the 

 Counties of Mayo and Sligo," by the Venerable Archdeacon Vers- 

 choyle, and communicated by Roderick lmpey Murchison, Esq. P.G.S. 

 was also begun. >v adt '1 



Nov. 21. — The reading of Archdeacon Verschoyle's paper, begun 

 at the meeting held on the 7th of November, was concluded. 



The author divides his memoir into two parts ; in the first he gives 

 a topographical description of the country, and in the second a detailed 

 account of the different formations of which it is composed. 



I. The district described is situated in the western part of the pro- 

 vince of Connaught, and is bounded on the N. and W. by the Atlantic. 

 Through the eastern portion a primary chain, called the Ox moun- 

 tains, having a mean height of 1300 feet, extends in a N.E. and S.W. 

 direction. The north side of the chain rises at a considerable angle, 

 and terminates in a series of abrupt, rocky peaks j but the plane which 

 forms the southern declivity is much more gradual in its inclination. 

 The principal passes are at Colloony, Lough Talt, and Foxford. The 

 formations of which the mountains consist are mica-slate, hornblende- 

 slate, and quartz- rock. Their bases are covered by a conglomerate 

 which the author considers to be the representative of the old red 

 sandstone; and on it reposes alternating strata of sandstone, and shale, 

 succeeded by carboniferous limestone. On the south of the chain 

 the limestone stretches towards Roscommon and Galway, joining the 

 great limestone field of Ireland; and on the N.W. it forms a plain, 

 extending from Sligo to the barony of Erris, where the Nephin group 

 rises from beneath it, being the commencement of the primary tract 

 reaching northward and westward to the ocean. Immense ridges of 

 water-worn pebbles occur in every portion of the district. The coast 

 presents for the greater part bold, abrupt precipices, formed of gneiss, 

 mica-slate, quartz-rock, and mountain limestone ; but in some places 

 it is low, and composed of a succession of sand-hills. 



II. In describing the formations comprising the district, the 

 author arranges them in the following descending order, — Carbo- 

 niferous limestone with beds of oolite, calcareous shale and grit, old 

 red sandstone or conglomerate, quartz-rock, gneiss, mica-slare, 

 hornblende-slate, granite, trap-rocks, porphyry, and basalt. An 

 abstract of his account of these formations is given in the Proceed- 

 ings of the Society. 



A communication was then read from the Rev. Adam Sedgwick, 

 V.P.G.S. and Woodwardian Professor in the University of Cam- 

 bridge, respecting certain fossil shells overlying the London clay in 

 the Isle of Sheppey. 



Mr. Sedgwick, in examining a series of fossils from the Isle of 

 Sheppey, lately presented to him, found several specimens differing 

 from the rest, both in their specific characters and state of preser- 

 vation. These shells were derived by Mr. Crow of Christ College, 

 Cambridge, from a bed in Warder Cliff, about 15 feet below the 

 surface of the ground, and had lately been laid bare by a small 

 land-slip. The bed in question is from 8 to 12 inches thick, and 

 the part exposed is not more than 20 feet in length, though there 



