S82 Geological Society, 



tiary strata of Antigua. Shells converted into chalcedony, and containing 

 agates in their cavities, occur near Exeter, in the whetstone pits of the 

 green-sand formation at Black Down Hill ; and shells, entirely converted to 

 red jasper, in sand of the same formation, at Little Haldon Hill. 



A paper was next read "On the Tertiary Fresh-water Formations of Aix, 

 in Provence, including the Coal field of Fuveau," by Roderick Impey Mur- 

 chison, Esq. Sec. G.S. F.R.S. &c., and Charles Lyell, Esq. For. Sec. G.S. 

 F.R.S. &c. ; with a description of fossil insects contained therein, by John 

 Curtis, Esq. F.L.S. 



The oldest and fundamental rock of this district is a highly inclined and 

 contorted secondary limestone, containing Belemnites, Gryphites, and Te- 

 rebratulae, on which is uncomformably deposited a vast fresh-water form- 

 ation, the relations of which are shown in a section from JN.E. to S. W. 

 The escarpment of white marl and limestone, N. E. of the town of Aix, is 

 first described in descending series. The upper beds, consisting of white 

 calcareous marls and marlstone, calcareo-silicious millstone and resinous 

 flint, contain the Potamides Lamarckii, Bulimus terebra and B. pygmse'us, 

 with a new species of Cyclas named C. gibbosa, and the subjacent strata run 

 out into a terrace, beneath which gypsum is extensively worked. Of these 

 beds (minutely detailed), some are peculiarly characterised by their abund- 

 ance of fossil fish, and others by a profusion of plants ; amongst which, Mr. 

 Lindley has recognised Flabellkria Lamanonw of M. Ad. Brongniart, and the 

 leaves of iaurus dulcis? Podocarpus macrophylla? and ^uxus balearica? 

 the terminal pinna of a leguminous plant, referable to iotese or Pha- 

 seoleae of Decandolle, the branch of a Thuja nearly related to T. articulata, 

 and what appears to be the fruit of some unknown plant, &c. In this upper 

 system of gypsum, the fossil insects occur exclusively in a finely laminated 

 bed of about 2 in. thick ; and still lower are two other ranges of gypsum, 

 the upper one of which alone is worked; and the marls associated therewith 

 contain nearly as great a quantity of fossil fish as those of the upper zone. 

 Beneath these are beds of white and pink-coloured marlstone and marl, in- 

 clined at 25° to 50°, and distinguished by Potamides Lamarckw, and a new 

 species of Cyclas, named C. A^quae Sextiae, and these pass downwards into a 

 red sandstone (Molasse) and a coarse conglomerate (Nagelfleu), the town of 

 Aix being situated at the base of the whole of the above series. 



In continuing the sectional line to the S. W., all the district between Aix 

 and Fuveau is made up of parallel ridges of fresh-water rocks ; the most 

 northerly containing red marl and fibrous gypsum, with Limnae^ae and 

 Planorbes (P. rotundatus) ; the intermediate range is of mere earthy lime- 

 stone, containing Limnae^ae and Gyrogonites, with micaceous sandstone and 

 shale ; and, lastly, the coal field of Fuveau is described as composed of grey, 

 blue, and black compact limestone and shale, with stony bituminous coal of 

 good quality ; the united thickness of the different seams of which amounts 

 to about 5 ft. The fossils characterising the carboniferous strata are two 

 new species of Cyclas, named C. cuneata and C. concinna, a Melania named 

 M. scalaris, Planorbis cornu, and a large species of U'nio. Casts of Gyro- 

 gonites were observed even in the coal itself j and the charcoal seemed, in 

 some instances, to be made up of a plant resembling Endogenites bacillare 

 of Brongniart. 



The authors remark that these lower members of this great tertiary de- 

 posit differ in character from any other fresh-water group examined by them 

 m central France, and have so much the aspect of the most ancient second- 

 ary rocks, that the presence alone of fluviatile and lacustrine shells, with 

 Gyrogonites, compelled them to recognise the comparatively recent date of 

 the whole group. 



This notice was accompanied by observations on the fossil insects men- 

 tioned in the preceding memoir, by John Curtis, Esq. F.L.S. These insects 

 are all of European forms, and are most of them referable to existing genera* 



