86 Colonel Silvertop on the Lacusti-ine Basins of 



posite ; and where its horizontal strata have been removed, the 

 surface of the ground presents an earthy calcareous mass, con- 

 taining the two cited univalves in great abundance. The latter 

 may be collected in any quantity in the earthy mass of the hill, 

 upon which a hermita or little chapel stands, about half a mile 

 from Teruel, beyond the arcos or aqueduct, as also in the higher 

 part of the first ascent on the road from Teruel to a village called 

 Campillo ; and, on the summit of both these hills, they are 

 found imbedded in thin strata of the limestone. The planorbis 

 is the most abundant shell, and, as well as the lymnea, of a 

 larger size than what were observed in the basin of Alhama. 

 They are, generally speaking, in the form of casts or moulds, 

 although a part of the remaining whitened shell is usually ob- 

 servable. 



This limestone forms an excellent and most durable building 

 stone, as is well exemplified in the beautiful arcos or aqueduct 

 at Teruel, of whose construction no record exists. 



In the subjacent bed of marl, which is more or less argil- 

 laceous, I observed, on approaching Teruel, by the Valen- 

 cia road, veins of laminar gypsum, and was informed that this 

 mineral is extensively quarried in the neighbourhood, but whe- 

 ther or not it belongs to this deposite, I cannot certify. Du- 

 ring my short visit to Teruel, I was unable to discover any 

 organic remains which might elucidate the geological relations 

 of this bed. The gypsum accompanying it, and its position be- 

 low the fresh-water limestone a a a, and above the secondary 

 limestone 3, present analogies with the gypsiferous marl depo- 

 sites in the basins of Baza and Alhama. 



At the points y y^ the transversal extremities of the basin of 

 Teruel, according to the line of the section sketch, the road 

 crosses over two bands, which, from the innumerable rounded 

 fragments of older rocks spread over the surface, as well as from 

 the lateral position of the former with respect to the basin, would 

 seem to indicate the action of some great body of water which 

 has swept along this area from north to south. 



It was in the first week of May 1828, I visited Teruel. The 

 summits of the higher hills in the elevated mountain tract, de- 

 signated Z, were covered with snow, as well as many of those in 

 the transition ridge 1 ; beyond the tertiary basin towards the 



