308 Geological Society : — 



run in various directions, some E. andW., others N.E. and S.W., 

 and others N. and S. They vary from 10 inches to i of an inch in 

 width ; in the largest veins the tin-ore occupies about 1 inch of one 

 side of the vein. Tlie veins nearly all occur in a great vein of fel- 

 spar and quartz ; which contains also ores of leaa, cojjper, zinc, iron, 

 and molybdena, associated with cryolite, fluorspar, zircon, &c. 



3. "On the Permian Chitonidse." By J. W. Kirkby, Esq. 

 Communicated by T. Davidson, Esq., F.R.S., F.G.S. 



After having fully noticed the progress of our knowledge respecting 

 the palaeozoic Chitons, and those of the Magnesian Limestone in 

 particular, the author described in detail the characters of Chiton 

 Loftusianus, King, and Chiton Howseanus, Kirkby, and a new species, 

 referred with some doubt to Chiton, C. (?) cordatus ; also Chiton 

 anticfcus, Howse, which Mr. Kirkby refers to the subgenus Chito- 

 nellus, as well as two new species, C. Hancockianus and C. distortus. 

 The specimens on which all these species have been determined 

 have been found in the Magnesian Limestone of the neighbourhood 

 of Sunderland, Durham, and chiefly in that of Tunstall Hill. 



The author particularly alluded to the great similarity that some 

 of the plates of these fossil Chitons have at first sight to Patellce and 

 CalyptrcetB, and recommended that especial care should therefore 

 always be taken in the determination of patelhform fossils. 



4. "On the Vegetable Structures in Coal." By 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 laminae 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 

 the 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 suhaerial decay of vegetable matter ; whilst 

 the compact coal is the product of \s«6a5Meo«s 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 Cryptogamous plants in the state of mineral 

 charcoal. Among these he mentions Lepidodendron and Vlodendron, 

 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 Calaniodendron ; 

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

 hitherto met with in the coal has belonged to Sigillarice. 



