on the Ground by tlte Foot of the Sow. 287 



generally did so, however. From the foregoing remarks, tlien, 

 it appears, that, on comparatively hard ground, where the im- 

 pressions are slight, the marks made may be either bisulcated, 

 or have in addition those of the posterior toes, on a horizontal 

 surface ; always bisulcated on ascending an inclined surface ; 

 but on descending the same, will generally present, in addition, 

 the marks of the posterior toes ; but this may or may not hap- 

 pen, according to the inclination of the surface. 



The general conclusion to be drawn from these observations 

 we think is, that the impressions made by the feet of the sow on 

 the ground, vary according to the softness, depth, and position 

 of the soil over which the animal may have passed ; and though 

 it seems to be true, that, in general, there are four impressions, 

 viz. of the two anterior and two posterior toes, still it seems 

 equally true that the same animal may, in certain circumstances, 

 leave a bisulcated impression, or that of the two anterior toes 

 only. 



April 182.9. 



On the Tertiary Fresh-noater Formations of Aix, in Provence, 

 including the Coal-field of Fuxieau. By Roderick Impey 

 MuRCHisoN, Esq., and Charles Lyell, Esq. junior, Secre- 

 taries to the Geological Society ; xoith a Description of Fossil 

 Insects, Shells and Plants, contained therein ; by John Cur- 

 tis, F. L. S. ; /. De C. Sowerby, Esq. F. L. S., atid J. Lind- 

 LEY, Esq., Professor of Botany in the London University. 

 Communicated by the Authors. 



W E are induced to offer the following sketch of the tertiary 

 district around Aix, in Provence, from finding that several of 

 the testacea and plants which we collected there last summer 

 belong to species hitherto undescribed ; and more particularly 

 that we may point out the geological position of certain fossil in- 

 sects, of which Mr Curtis has added some interesting figures, 

 and a description. A portion of this district has already been 

 described by M. Bertrand Geslin *, and as a still more detailed 

 account of the whole country is shortly expected from the pen 



" Sur le Basuin Gyiwoux d'Aix, &c. Mem. de ilist. Nat. dc Paris, torn. 1. 

 part 2. p. 273. 



1 u2 



