254 Proceedings of the Royal Physical Society. 
Sigularia Brardiz, Brongt., passed by gradual transitions into 
Sigilaria spinulosa, Germar, and that this latter plant was 
therefore only a condition of the former! This discovery 
showed that at least some of the Clathrarian and Leioder- 
marian Sigillarie were merely different conditions of the 
same species. And further, in certain conditions, the leaf- 
scars of Sigillaria Brardit sometimes assume an arrangement 
having a superficial resemblance to the Favularian group. 
This is seen to some extent in the upper portion of my 
Fig. 1. 
Shortly after the announcement by Dr Weiss of the identity 
of Sigillaria spinulosa, Germar, with Sigillaria Brardii, 
Brongt., Mons. Zeiller figured several specimens of Sigillaria 
Brardu, one of which showed the organic union of the 
Clathrarian and Leiodermarian forms on the same specimen, 
—the upper part of this specimen corresponding absolutely 
with Sigillaria Brardii, Brongt., and the lower portion with 
Sigillaria spinulosa, Germar. It was also further shown that 
Sigillaria rhomboidea, Brongt., only represents an intermediate 
condition. The specimen which I figure on Plate VIL, Fig. 1, 
shows the union of Sigillaria Brardit, Brongt., and Sigillaria 
denudata, Gopp., on the same specimen. 
A most elaborate memoir on the Clathrarian Sigillaria, 
commenced by the late Dr EK. Weiss, was issued in 1893 
under the joint authorship of Dr E. Weiss and Dr T. Sterzel. 
It forms part ii. of Die Sigillarien d. preuss. Steink.-u.-Rothl.- 
Gebiete® The accuracy of description, and the correctness 
and beauty of the plates which accompany the letterpress, 
make this work of the greatest value to all students of this 
most difficult class of fossil plants. Whatever opinion one 
may hold as to the system of nomenclature adopted by these 
authors in their work, they never leave any doubt as to the 
form of the plant to which their names and descriptions 
refer. 
1 Zeitsch. d. deut. geol. Gesell., 1888, p. 566. 
? Bull. Soc. géol. d. France, sér. 3, vol. xvii., p. 603, pl. xiv., fig. 1, 1889. 
* Die Sigillarien der preussischen Steinkohlen-und-Rothliegenden-Gebiete, 
II. Die Gruppe der sub-Sigillarien, Abhandl. d. Konig. Preuss. geol. Landes- 
anstalt, Neue Folge, Heft 2, Berlin, 1893, pp. i-xvi, 1-255, with atlas of 
twenty-eight plates, 
