Geoloc/ical iSocielij. 439 



7. The mandibular arc is primitively attached behind the point of 

 exit from the skull, of the third division of the fifth nerve. 



8. The premaxilla is originally totally distinct from the palato- 

 maxillary arcade. 



9. The pectoral arch is originally totally distinct from the skull. 

 Startiiig on this basis, it might not be difficult to show that the 



perfectly ossified skull is divisible into a series of segments, whose 

 analogy with vertebrae is closer the nearer they lie to the occipital 

 region ; but the relation is an analogy and not an affinity, and riiese 

 cephalic sclerotomes are not vertebrae. 



GEOLOGICAL SOCIETY. 



March 9, 1859.— Sir C. Lyell, V.P., in the Chair. 



" On the Vegetable Structures in Coal." Bv J. W. Dawson, 

 LL.D., F.G.S.. Principal of M'Gill College, Montreal. 



After referring to the labours of others in the elucidation of the 

 history of coal, the author remarks that in ordinary bituminous coal 

 we recognize by the unaided eye laminse of a compact and more or 

 less lustrous appearance, separated by uneven films and layers of 

 fibrous anthracite or mineral charcoal. As these two kinds of 

 material differ to some extent in origin and state of preservation, 

 and in the methods of study applicable to them, he proceeds to treat 

 of his subject under two heads: — 1st. The structures preserved in 

 tlie state of mineral charcoal. This substance consists of fragments 

 of prosenchymatous and vasiform tissues in a carbonized state, 

 somewhat flattened by pressure, and more or less impregnated with 

 bituminous and mineral matters derived from the surrounding mass. 

 It has resulted from the suhuiirial decay of vegetable matter ; whilst 

 the compact coal is the product of subaqueous putrefaction, modified 

 by heat and exposure to air. The author proceeded (after describing 

 the methods used by him in examining mineral charcoal and coal) 

 to describe the tissues of Cryptogaraous plants in the state of mineral 

 charcoal. Among these he mentions LepidodencJron and Ulodendron, 

 also disintegrated vascular bundles from the petioles of Ferns, the 

 veins of Stigmarian leaves, and from some roots or stipes. He then 

 describes tissues of Gymnospermous plants in the state of mineral 

 charcoal ; especially wood with discigerous fibres and also with 

 scalariform tissue, such as that of Stigmaria and Culamodendron ; 

 and the author remarks that probably the so-called cycadeous tissue 

 hitherto met with in the coal has belonged to Sicjillarice. 



The next chief heading of the paper has reference to structures 

 preserved in the layers of compact coal, which constitutes a far 

 larger proportion of the mass than the mineral charcoal does. The 

 laminae of pitch- or cherry-coal, says Dr. Dawson, when carefully 

 traced over the surfaces of accumulation, are found to present the 

 outline of flattened trunks. This is also true to a certain extent of 

 the finer varieties of slate-coal ; but the coarse coal appears to con- 

 sist of extensive laminse of disintegrated vegetable matter mixed 

 with mud. When the coal (especially the more shaly varieties) is 



