FOREIGN CORRESPONDENCE. 



205 



What is very remarkable is, that these Tertiary coals are exactly 

 like those of the coal-measures proper, whilst the fossil fuel of the 

 same age found in Oregon and Washington is non-bituminous. 



It would appear that we have in the coal of Chirigui, formed in the 

 Tertiary clays under the tropics, a modern instance of the con- 

 ditions in which the coal beds in the coal-measures have been produced, 

 thence results the resemblance of these Tertiary coals with those of 

 the coal-measures proper, which, beyond a doubt, were formed under 

 a tropical temperature. 



An interesting geological fact is that the coal-measures have 

 not yet been traced in South America. All the beds there observed 

 belong to the Tertiary epoch. 



On a means of recognizing the Shores of Ancient Seas. 



M. Marcel de Serres, in a recent letter on a means of 

 recognizing the ancient shores of the seas of geological epochs, 

 after referring to his studies on the boring-mollusca, points 

 out a locality near St. Apolis, in the neighbourhood of Pezenas 

 as very interesting. There the cretaceous rocks, which run parallel 

 with and adjoin the Mediterranean, are full of thimble-shaped cavities, 

 the work of these mollusca. On the north side of the mountain 

 nothing of the kind is seen ; the rocks thus perforated are not elevated 

 above the level of the soil beyond the point at which they have 

 been bored, and the miocene beds rest on them. 



Knowing as we do that the boring-mollusca are to be found in the 

 vicinity of the coast-line, are we not justified in looking upon this 

 spot as an old sea- shore ? M. Marcel proceeds : — 



" I am now endeavouring, by the consideration of similar facts, 

 to determine, by means of the rocks attacked by these animals, the 

 localities which mark the extent of the ancient seas, and I believe I 

 have succeeded in a locality now well known in a geological point of 

 view — I mean the basin of Neffier. There the palaeozoic beds are 

 bounded on the south-east by the tertiary marine formations ; these 

 are composed in certain localities of masses of polyps of the genus 

 Astrea, pierced by a great number of Modiolse and Petricolse, and 

 others. 



As these different species recede but little from the coast, and the 

 polyps occupy the same position as they did in the same sea, they 

 seem to represent its ancient margin ; a fact confirmed by their 

 position relatively to the Mediterranean, near which these beds are 

 situated. 



On the Tertiaries of Bigorre. 



M. Leymerie has communicated to the French Academy a note on 

 the Tertiaries of Bigorre, principally studied in the valley of the 

 Adour. From this note, which is very interesting, we extract the 

 following description of the locality mentioned ; — 



