766 MR ROBERT KIDSTON ON THE FOSSIL PLANTS OF 



the leaf scar as in PI. III. fig. 26, but the absence of this elevation on this and the 

 succeeding examples is evidently the result of pressure. The leaf scars on this specimen 

 are scarcely so wide as the rib, and from their lateral angles two little lines run down- 

 wards, and in some cases seem to bend inwards and meet, cutting off an oval area. At 

 first sight one might think this specimen specifically distinct from the other examples of 

 Sigillaria Canobiana described here, but the upper part of the fossil marked a shows 

 the ordinary form of the species, though towards the middle, and especially to the left, 

 the leaf scars become closer and appear as if separated into compartments, but at the 

 base at B they again begin to assume the normal condition. Such approximation of the 

 leaf scars on the stems of Sigillarix is no uncommon occurrence. 



Plate IV. fig. 31 is portion of another specimen enlarged two times, and fig. 32 shows 

 an outline sketch of a leaf scar and portion of a rib. The distinctive characters of the 

 species are well shown on this example. The general form of the leaf scar is rhomboidal, 

 the upper margin is distinctly notched, the lower is rounded, while the lateral angles 

 are prominent. The leaf scars occupy the whole width of the rib, which at this 

 point widens out. Immediately below the leaf scar the rib narrows gradually till it 

 reaches the scar beneath, where it slightly expands again, though it still remains con- 

 siderably narrower than the leaf scar against which it terminates. The margin of the 

 interfoliar region of the rib thus forms a sigmoid line, the sinus of whose curve is 

 occupied by the inflated portion of the neighbouring rib. The transverse wrinkling on 

 the surface of the rib, which extends almost over the whole width, is strongest immedi- 

 ately above the leaf scar, and becomes more feeble as it is traced upwards, till below the 

 next higher leaf scar it is absent or only very slightly shown. The leaf scars are here 

 more distant than on the specimens already described, being distant from each other 

 about the space of two leaf scars. 



Plate V. fig. 45, natural size, portion enlarged two times given at fig. 46, and outline 

 sketch of scar at fig. 47. 



The leaf scars on this specimen are more truly rhomboidal than on some of the 

 examples already described, and are slightly more distantly placed. As in all cases 

 except that shown on Plate IV. fig. 33, they occupy the whole width of the rib, which 

 at their point of insertion is widened. 



Fig. 45 illustrates well the inflation of the rib, which, a short distance below the scar, 

 becomes contracted. The margin of the upper part of the rib between the leaf scars is 

 convex, but it afterwards runs almost straight till it abuts on the scar below it. The 

 sigmoid curve is not so prominent as in Plate IV. fig. 31. The transverse wrinkling on 

 the surface of the interfoliar cortex is similar to that of the specimens already described. 



Remarks. — There is no species of Sigillaria, as far as I am aware, with which 

 Sigillaria Canobiana could be mistaken. Its nearest ally is probably Sigillaria poly- 

 ploca, Boulay.* The ribs in this species are also inflated, but their widest part is a 



* Sigillaria polyploca, Boulay, Terr, houil. du Nord de la France, p. 47, pi. ii. fig. 8, 1876. See also Zeiller, Flore 

 foss. bassin houil. d. Valen., p. 450, pi. Ixxxii. figs. 7-8. 



