TRANSACTIONS OF THE SECTIONS. 87 



On a Fossil Mussel-sliell found in Drift in Irelmid. 

 By Eugene A. Conavell, M.B.I.A. 



The author exhibited a marine mussel-shell measui-ing 3^ inches in length, \\ inch 

 at its broadest part, and ^ inch in internal depth, still in as perfect a state of preserva- 

 tion as when worn by its ancient occupant. An oblong-shaped pearly excrescence, 

 about the eighth of an inch in length, is attached to the centre of the interior part 

 of the shell, and some of the fine sand in which this bivalvular fossil has lain 

 deposited for ages stiU adheres to the inside of it. It was pronounced to be a spe- 

 cimen of the Mtjtilus vulf/aris inhabiting our present British seas. It was dug up on 

 Saturday, August 22, 1868, by a labourer employed by the author to raise gi'avel 

 for walks, from the bottom ot an ancient sand-hill, or escar, within a quarter of a 

 mile of the town of Trim, in a portion of the groimds of the District Model National 

 Schools, established there by the Commissioners of National Education in 1849. This 

 fossil was found resting under the regis of a large boulder, which in some degree 

 may account for its very peifect state of preservation, and in a situation at present 

 25 miles from the nearest sea-coast, and about 200 feet above the present sea-level. 

 And here the consideration arises, how vast must be the period of time that has 

 elapsed since the sand and gi-avel in which this shell has been imbedded were 

 rolled about by the waters of an ocean which has retreated at least 25 miles from 

 this spot ; and, still more, how vastness of time must be piled on vastness since the 

 lowest of the stratified rocks under this old escar was deposited; and how many 

 times " Old Ocean " must have advanced on this land and again retreated to sub- 

 merge other lands ! 



The gravel, or drift, in which it was found consists of dark Carboniferous limestone 

 pebbles, utterly devoid of flint nodules, thus proving the antiquity of the drift, and 

 rests upon a portion of that large bed of Carboniferous limestone-rock which occupies 

 the greater part of the middle of the island. 



The hills and ridges of sand and gTavel, so conspicuous across the centi-e of Ire- 

 land, are supposed to have been formed in the eddies of opposing and conflicting 

 currents, at a period when the present dry land was the bed of an ocean. Sometimes 

 they are to be seen in single heaps, and at other times in narrow ridges, of all degrees 

 of fineness and coarseness of material, varying in height from 20 to 80 feet, and ex- 

 tending in some parts from 1 to 20 miles in length. The prevailing direction of the 

 line of subsidence of these ranges of drift in Ii'eland, rimning, as they generally do, 

 nearly due east and west, has always appeared to the author to be in some degree 

 connected with the rotation of the earth on its axis dm-ing the process of their being 

 accumulated on the ocean-bed. 



■ These hiUs of gravel are popularly known (and only in Ireland) by the name of 

 escars, from a purely primitive Irish word (eiscif) meaning a ridge of high land, but 

 generally applied to a sandy ridge. The term, usually takmg the form of esker (as 

 it is pronounced), is the name of about fifty townlands in Ireland, and combines to 

 form the names of many other places, more especially across the middle than in 

 either the_ north or the south of Ireland. Although the nomenclatm-e of escar for 

 sand-hiU is peculiar to Ireland, it is curious to remark that we have now a town 

 situated on a sand-hill, at the base of the Pyrenees, called Escar, which is a Basque 

 name ; and it is understood that the Basques have had a language peculiarly then- 

 own, but they have also had easy communication vsdth Ireland. 

 . Not far from, or indeed belonging to, the escar in which this shell was found, 

 there is a line of gravel hills extending, with slight interruption, from Dublin to 

 Galway, called Esker-Riada ; and this is the most historically celebrated escar in 

 Ireland, having been fixed upon as the boundary between the northern and the 

 southern half of Ireland when the country was divided, in the second century, 

 between Owen More and Conn of "The Hundred Battles." This ridge probably 

 has its name, as the late eminent Irish scholar. Professor Eugene O'Cimy, thought, 

 from the chariots that used to run on it. 



On the Occurrence of a large Deposit of Terra Cotta Clay at Watcombc, 

 Torquay. By Robert Etheeidge, F.G.S. 



