163 



but published lists, which deserve the greatest confidence, establish 

 beyond^ all doubt that those species which abound in a formation 

 belong to various beds, and that those species which at one locality 

 are most numerous fail altogether in another. 



Mr, Mammatt, one of our Fellows, has embodied the result of 

 fortyyears experience in a splendid Work on the Coal-field of Ashby 

 de la Zouch, illustrated with beautiful engravings. 



It is a work of considerable labour, and independently of its local 

 interest, contains some remarks on fissures, joints, and " slines," 

 which coming from a practical observer are well entitled to atten- 

 tion. It is to be regretted that the specimens from which the draw- 

 ings were taken have been too frequently impertiect or indistinct. In 

 other branches of natural history, so intimate are the relations of the 

 several parts, that from the examination of an unknown tooth and 

 a few other bones, the expert physiologist has been enabled in some 

 instances to construct in imagination an unknown animal, the fidelity 

 of which, to nature, subsequent discoveries have established. The 

 laws which determine vegetable forms are more indefinite and ob- 

 scure; if fragments of plants are to be engraved, they require to be 

 selected with great judgement, and should be confined to those 

 parts of the object which are best defined and most characteristic. 

 Seen from another point of view, however, these plates become 

 immediately valuable 3 for though the objects engraved were too 

 indistinct perhaps to enable us to determine the genus, class, or 

 order to which they belong, a correct delineation of them may be 

 sufficient to enable us to identify them with objects found in other 

 coal-fields, perhaps in very distant parts of the world. 



The author adopted at an early period the opinion that " Strata 

 are characterized by their Fossils," and he appears to think, that 

 in the coal-field under his consideration, each bed of shale has 

 vegetable impressions of its own. By the precision with which the 

 work is executed, the justice of this opinion is at once put to the 

 test ; the successive strata are numbered in regular order, and the 

 names of the plants (where they have names) are attached to the 

 numbers to which they respectively belong. Now, in looking over 

 the list, with a view to the determination of the question before us, 

 I observe Stigmariajucoides at No. 25, 55, 223, 232 ; Sigillaria Or- 

 ganum at No. 37 and 118; Sigillaria oculata at No. 74 and 79; Aste- 

 rophyllites longifolia at No. 16, 330, and 370 3 and Neuropteris gi- 

 gantea at No. 112, 147, 249 a, and 406. 



A series of Vegetable Impressions transmitted to us by Mr. De 

 la Beche has given rise to a good deal of discussion. The plants 

 have been examined by Mr. Lindley, and identified at once with 

 those usually found in the Newcastle and other regular coal-fields ; 

 they form the roof of certain beds of coal or culm which have long 

 since been observed and worked in the neighbourhood of Bideford 

 in Devonshire, and extend from the shore inland to the distance 

 of about fourteen miles, being about three quarters of a mile in 

 breadth. Along the coast very distinct sections are exposed, both 

 of these beds and their associates. The associated beds have hi- 



