no Colonel Silvertop 07i the Lacustrine Basins of 



water limestone begin to cap one or two eminences near the Ven- 

 ta de Huelma, and again, in a more considerable but insulated 

 mass, crown a portion of the hill previous to the descent to Ca- 

 cin. Immediately under this mass, on the Cacin side, as also 

 along the right bank of the rivulet at the bottom of the descent, 

 gypsum is observed in great abundance, as has been already no- 

 ticed. It would, therefore, appear that this gypsum formation 

 is immediately subjacent to the fresh-water or compact paludinae 

 limestone, which, as will shortly be seen, becomes the predomi- 

 nating and superior * rock in the southern portion of the basin, 

 and constitutes a ridge of considerable elevation between Cacin 

 and Alhama. 



At the commencement of the ascent beyond Cacin to this 

 ridge, gypsum imbedded in marl is again observed ; but higher 

 up it is succeeded by horizontal strata of compact, somewhat 

 vesicular limestone, of a dingy whitish colour, containing here 

 and there casts or moulds of paludinae. Still higher up the 

 ascent, and subsequently crowning in a partial manner its sum- 

 mit, the marly limestone, formed of broken shells, and distin- 

 guished by the presence of planorbes, as \^11 as of lymneae 

 and paludinae, makes its appearance, overlying the former. . 

 These two limestones continue to be observed in the same order 

 of superposition nearly to the bottom of a broad denuded hollow 

 in the ridge, and during the subsequent ascent. The highest 

 part of the ridge presents an irregular sort of table-land, covered 

 ♦with wild plants and shrubs. Its total width is between seven 

 and eight miles. In the long gradual descent to the rivulet of 

 Alhama, cultivation generally prevents the subjacent beds from 

 being seen until near its termination, when a few horizontal strata 

 of calcareous sandstone are observed, whose geognostical relations 

 will soon be made evident. The road then passes a bridge over 

 the last mentioned stream, which has worked its way or pene- 

 trated at this point through a little insulated mass of secondary 

 nummulite" limestone, manifesting in some places, as I have fre- 

 quently observed in tliis rock, a semblance of brecciated structure, 

 and following up its left bank for about a mile, winds to the right, 

 and, between escarpments of calcareous sandstone, whose hori- 



• A more modern marly limestone partially overlies it, as will be imme- 

 diately noticed. 



