178 FOSSIL PLANTS. 



such examples as those just mentioned, though, if at all possible, one is 

 naturally anxious to correlate them to the species of which they are decorti- 

 cated examples. 



The small figure which Buckland gives of his Ulodendron Lucasii is not all 

 that could be desired for a satisfactory determination, but from the form of 

 the few leaf-scars, as shown on his figure, there is little reason to doubt that 

 this species should also be placed under Sigillaria discophora. 



I am unable to discover any point by which Ulodendron pumilum, 

 Carruthers, can be distinguished from Sigillaria discophora. The specimen 

 from which Mr. Carruthers' figure is taken is in the Collection, and shows 

 very well the Sigillarian form of the leaf-scars. This fossil is somewhat 

 smaller in all its parts than Konig's example, but this difference is entirely 

 dependent on age. A figure agreeing in all essentials with that of Mr. 

 Carruthers, and which I also refer to Sigillaria discophora, had previously 

 been published by Dawson in his Acadian Geology (2nd ed. fig. 170^, 

 p. 455, 1868) under the name of Lepidophloios parvus. What I believe to be 

 only an older state of Lepidophloios parvus is the Lepidophloios tetragonus, 

 Dawson (l.c., p. 455 ; Quart. Journ. Geol. Soc. vol. xxii. pi. x. fig. 49). 

 On a large specimens of Sigillaria discophora, from the Coal Measures, Old 

 Sauchie, Clackmannanshire, in my own Collection, some of the leaf-scars 

 agree entirely with those of Dawson's Lepidophloios tetragonus. 



Halonia disticha, Morris, must also be united with Sigillaria discophora. 

 Specimens preserved in the round, similar to his figure, are by no means 

 uncommon. The presence of only two rows of large scars on his fossil is 

 sufficient to remove it from Halonia (Lepidophloios), and the other characters 

 of the specimen show its true place to be here. 



Geinitz (Vers. d. Steinkf. in Sachsen, p. 38) appears to have misunderstood 

 the true nature of Lindley and Hutton's genus Bothrodendron, for under the 

 name of Halonia punctata he includes different fossils. 



Lepidodendron salebrosum and Sigillaria perplexa, Wood, are only fragments 

 of Sigillaria discophora. Both in Sigillaria perplexa and in the figure given 

 under the name of Sigillaria Menardi by Lesquereux, the longitudinal clefts 

 which appear in the bark of old examples are well seen. A similar vertical 

 splitting of the bark also takes place in the succeeding species (Sigillaria 

 Taylori, Carruthers, sp.), and has already been pointed out as occurring in 

 Lepidodendron Veltheimianum (=Ulodendron parmatum and U. commutatum). 



One of the most interesting figures of this species has been given by 

 Eomer (Palaeontographica, voL ix. pi. xii. fig. 7) under the name of Sigillaria 

 Preuiana. He says of his plant (p. 42) : " The leaf -cushions stand as in 

 Lepidodendron, in oblique rows ; they are rhomboidal or six-sided, as long as 

 broad, slightly elevated, and show above the middle a round scar, on each 

 side of which is a lunate cicatricule. The leaf-scar is almost as large as the 

 leaf-cushion. 



In other words, there is in Sigillaria Preniana, which is synonymous with 

 Sigillaria discophora, a Clathrarian-Sigillaria. In this section of Sigillaria 

 the scars to which the leaves articulate are placed upon slightly elevated 

 cushions, which in their structure are comparable to the cushions to which 

 the leaves of Lepidophloios are attached. In the compressed condition these 

 Clathrarian-Sigillaria might lead one to suppose that the vascular-scar was 

 surrounded by a ' field " as in Lepidodendron, but this appearance is alto- 

 gether due to mechanical causes, and does not represent a parallel structure. 

 In Lepidodendron the leaf base is not only attached to the vascular impression 

 of the leaf -scar, but to the whole area of the "field." In Sigillaria the leaf 

 is only attached to the vascular-scar, which is not surrounded by a " field." 



I have seen many well-preserved specimens of Sigillaria discophora, with 

 * h . e leaf -scars identical with those described by Homer as occurring on his 

 bigMana Preuiana, and were it not for the presence of the large Ulodendroid- 

 scars on these specimens they could not have been distinguished from his plant. 

 Hence, when Sigillaria Preuiana agrees in all its characters with undoubted 



