SOUTH-WEST IRELAND. 191 



materials for the latter ; or, on the other hand, as 

 estuarine deposits may contain pieces of the upper 

 and lower rocks, and as the river gravels may be 

 formed from them, the latter gravels may thus 

 contain innumerable different kinds of rocks. 



Estuary muds, and some sands, often contain 

 marine shells, while gravels and peaty deposits 

 seldom do. Terrestrial and fresh-water shells may 

 also occur, especially in the gravels formed at the 

 margins of the estuary. Thus, in Killary Harbour, in 

 the accumulations at Leenaun, and at the mouths of 

 the Bundorragha and Derrynasliggaun streams, there 

 are more fresh-water and terrestrial than marine 

 shells, while the bones of land animals are not un- 

 common ; all being carried down by freshets in the 

 rivers, and deposited in the estuary. The estuary 

 of the Shannon, in the neighbourhood of Limerick, 

 formerly extended much farther than at present, 

 it having been margined by mud-flats, corcasses, 

 swamps, and salt-marshes, which are now reclaimed, 

 some within the last few years. These evidently 

 were estuary deposits, formed very recently ; as 

 before they were embanked they were covered during 

 every spring-tide. In some places marine shells are 

 very common ; but associated with them are the 

 horns and bones, and sometimes even entire skeletons, 

 of the elk, reindeer, red deer, <fec. Some of these 

 bones were evidently carried down into their present 



