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PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Dec. 4, 



cells in the direction of the growth ; but these appearances may be 

 due to different degrees of preservation, and Mr. Salter has seen 

 specimens of D. folium in which they are quite conspicuous, and 

 believes the species identical. 

 Locality. Little Queensberry. 



5. D. foliaceus, Murchison, sp.? 



Pl. I. fig. 13. Natural size. 



(Murchison, Sil. Syst. pl. 26. f. 3 ?) G. folium, Salter, Geol. Journ. 

 vol. v. pl. 1. f. 5. See also G. palmeus, Barrande, loc. cit. pl. 3. 

 f. 1-7. 



This form is subject to great variations, more particularly as re- 

 gards its relative breadth and length. Many of the Dumfriesshire 

 specimens have a fusiform appearance, and their breadth generally 

 exceeds those figured by M. Barrande *. In an individual specimen 

 of about three-fourths of an inch in length, the total breadth where 

 widest exceeded one-fifth of an inch. In some instances the apex 

 does not terminate by tapering, but abruptly. The central axis, al- 

 though but thin, is commonly very distinct ; and it appears to have 

 been somewhat flattened. There is properly speaking no space be- 

 tween this axis and the base of the cells, which seem to take their rise 

 immediately from the side of the axis ; they are directed upwards 

 and adhere to each other through their whole length. Their mouths 

 are distinct and straight, and have no appendage attached thereto. 

 The number of cells in a line is three, and this distance appears 

 uniform both at the base and apex. The nature of the external co- 

 vering of this species, at least from the Dumfriesshire specimens, 

 cannot be determined, owing to the fossils being in the form of iron 

 pyrites. The species occurs in great abundance both at Dobbs Linn, 

 and also at the base of Hartfell, where it is associated with the pre- 

 ceding. 



Scalariform or edge views of this or other species. 

 Pl. I. fig. 14. 



Independent of the variations to which the last species is subject, 

 there are other circumstances which, in common with all others 

 of this genus, greatly modify it. These are in general the result of 

 the fossil being crushed in such a manner as to give a lateral view. 

 From this we have the various scalariform appearances on which have 

 been founded such species as G. scalaris, Linn., but which M. Bar- 

 rande in his * Graptolites de Boheme ' has shown to be only modifi- 

 cations arising from lateral pressure. Prof. M'Coy had also inde- 

 pendently arrived at the same conclusion, which he lately published 

 in the 'Annals and Mag. of Nat. Hist.' vol. vi. p. 272*. 



* The G. foliaceus, Murchison, is so imperfect a specimen, that it is almost 

 useless to refer to it till better specimens be discovered in the same locality. 



