BRITISH ASSOCIATION MEETING. 



307 



Tlie Wed R'liir terminates in tlie Chott Melr'hir, a depression probably 

 eighty feet below tlie Mediterranean sea-level, and the lowest point of the 

 M^hole Sahara. This basin extends eastwards to the Chott el Melah (Lake Tri- 

 tonis), at a greater elevation, but yet scarcely rising to the sea-level, from 

 which it is separated by some thirty miles of sand-hills and rocks. 



Proceeding northwards of the Melr'hir, we rapidly lose all traces of the 

 dilavian deposits, and come upon the chalk, chalk-marl, and greensand in 

 regular succession, dipping generally southwards. The three southernmost 

 ridges of the Mons Aures, viz., the Djebel Checha, the Dj. Khaddon, and 

 Dj. Amar, present us with these three stages of the cretaceous group in 

 order. 



When we advance to the north of Biskra, the boundary between the Till and 

 the eastern Saiiara, the mountains are composed of masses of nummulite lime- 

 stone, with bands of gypsum and occasional irruptions of rock-salt, mixed with 

 layers of marl. One of these mountains of rock-salt has been described long 

 since by Dr. Shaw — that of El Outaia. 



There are many salt deposits, sometimes masses of isolated rock-salt, per- 

 fectly pure, of many hundred yards in circumference, as at Hadjera el Melil, 

 (or Rochers de Sal), more frequently in the form of layers or incrustations on 

 the plains near the Chotts, or beds of evaporated lakes. Some of the isolated 

 rock-salt hills have been suggested to have been eruptions of argillaceous mud, 

 gypsum, and rock-salt across the secondary and tertiary deposits. 



In such a country as the Sahara, we cannot expect to find much mineral 

 wealth, beyond the salt, gypsum, and natron. There is a quarry of oxide of 

 manganese in the Djebel Trisgrarine, traces of lignite and carbonized trees at 

 Ain el Ibel, and may hot springs — some pure, others strongly impregnated with 

 chlorine. The temperature of one of these I found to be one hundred and 

 twenty-five degrees Fahrenheit, of others from seventy-five to ninety-five degrees 

 Fahrenheit. In one of the latter were swarms of a little fish, Cypruiodon 

 clispar, also found in the warm springs of Egypt. 



ON THE INVERTEBEATE FAUNA OF THE LOWER OOLITES OF 

 OXFORDSHIRE. 



By L F. White aves, F.G.S. 



The author remarked that, although the physical geology of the neighbour- 

 hood of Oxford was, with some exceptions, tolerably well understood, com- 

 paratively little was known with respect to its palaeontology, especially that 

 part relating to the invertebrate division of the animal kingdom. The only ex- 

 ception he was aware of was a detailed list of the fossils of the Stonesfield 

 slate in the volume of Oxford Essays for 1855, by Professor Phillips, and to 

 this list the author was enabled to add twenty-seven species of sheUs, which ho 

 enumerated. 



Near the Kirtlington Station, on the Great Western Railway, several 

 fine sections of the upper beds of the Great Oolite are remarkably well 

 exibited ; and in deep cuttings on the Oxford, Worcester, and Wolverhampton 

 railway, between the Handborough and Charlbury Si ations, the lower beds of 

 the same formation may be conveniently studied. The fossils procured from 

 these beds, including the Stonesfield-slate, were one hundred and thirty-five 

 species, of which one hundred and twenty-eight were shells, four echinodermata, 

 three corals, and one Bryozoon. This list seemed to the author especially 

 interesting, as tending to remove the isolation of the Minchinhampton fauna, 

 and to prove that shells, &c,, previously detected only on the Cotswolds, were 



