GEOLOGY. 353 



arch, as in the Megatherium and Diprotodon, and exhibits an extraordinary 

 width of the zygomatie arches. The skull, at its broadest part, across the 

 zygomata, is fifteen inches wide, and is eighteen inches long. In Diprotodon, 

 the skull is about three feet long by one foot eight inches broad : so that, 

 Avhile the latter must have had a face somewhat like that of the Kangaroo, 

 the Zygomaturus more resembled the "Wombat in the face and head. 



^ 



ON THE VEGETABLE STRUCTURE OF COAL. 



The following is an abstract of a paper recently presented to the Geologi- 

 cal Society (London), by Prof. J. W. Dawson, of M'Gill College, Montreal: 



After referring to the labors of others in the elucidation of the history of 

 coal, the author remarks, that in ordinary bituminous coal we recognize, by 

 the unaided eye, lamina; of a compact and more or le.ss lustrous appearance, 

 separated by uneven films and layers of fibrous anthracite or mineral char- 

 coal. 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 pre- 

 served in the state of mineral charcoal. This substance consists of frag- 

 ments of prosenchymatous and vasiform tissues in a carbonized state, some- 

 what flattened by pressure, and more or less impregnated with bituminous 

 and mineral matters derived from the surrounding mass. It has resulted 

 from the subaerial 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 examin- 

 ing mineral charcoal and coal) to describe the tissues of Cryptogamous 

 plants in the state of mineral charcoal. Among these he mentions Lepido- 

 dcndron and Ulod^dron, also disintegrated vascular bundles from the petioles 

 of Ferns, the veins of Stigmarian leaves, and from some roots or stripes. 

 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 CuJamodendron ; and the author re- 

 marks that probably the so-called cycadeous tissue hitherto met with in the 

 coal has belonged to Sigillariw. The next chief heading of the paper has 

 reference to structures preserved in the layers of compact coal, which consti- 

 tute a far larger proportion of the mass than the mineral charcoal does. 

 The lamina? of pitch or cherry-coal, says Dr. Dawson, when carefully traced 

 over the surfaces of accumulation, ai-e found to present the outline of flat- 

 tened trunks. This is also true, to a certain extent, of the finer varieties of 

 slate-coal; but the coarse coal appears to consist of extensive lamina? of dis- 

 integrated vegetable matter mixed with mud. When the coal (especially 

 the more shaly varieties) is held obliquely under a strong light, in the man- 

 ner recommended by Goeppert, the surfaces of the lamina? of coal present 

 the forms of many well-known coal-plants, as Sigillaria, Stigmaria, Poacites, 

 (or Nccggfra thin), Lt-pidodendron, Wodendron, and rough bark, perhaps of 

 Conifers. When the coal is traced upward into the roof-shales, we often 

 find the lamina? of compact coal represented by flattened coaly trunks and 

 leaves, now rendered distinct by being separated by clay. The relation of 

 erect trees to the mass of the coal, and the state of preservation in which 

 the wood and bark of these ti-ces occur, the microscopic appearance of 

 coal, the abundance of cortical tissue in the coal, associated with remains 

 of herbaceous plants, leaves, etc., are next treated of. 



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