THE CARBONIFEROUS ROCKS OF CANONBIE, DUMFRIESSHIRE, ETC. 797 



in no respect from Sigillaria elegans, of which I regard Sigillaria minima to be a 

 young condition. 



Sigillaria elegantula, Weiss, seems to me also to be only a form of Sigillaria elegans. 

 The presence of the keels from the two lateral or basal angles of the leaf scar is not a 

 constant character, which is one of the chief specific distinctions. Sometimes one keel 

 only is present, and on a neighbouring leaf cushion they may be entirely absent. Even 

 if the keels were always present, it seems too slight a character on which to found 

 a species. 



On a specimen of Sigillaria elegantula from Konigsgrube, Aachen, received from 

 the late Dr Weiss, few of the cushions show any trace of a keel descending from the 

 lower angles of the leaf scar. 



The specimen figured by Potonie (I.e.) under the name of Sigillaria elegantula shows 

 no sign of the keels, and seems to be a typical example of Sigillaria elegans. 



Localities C, D. Not uncommon. 



Pinakodendron, Weiss. 



1893. Pinakodendron, Weiss, Die Sigillarien d. preuss. Steinkohlen-und Rothliegenden Gebiete, ii. 

 Gruppe, der Subsigilkirien, — Abhandl. d. Kbing. preuss. geol. Landesanstalt, Neue Folge, Heft 

 2, p. 61. 



Description. — Stems with small distant quincuncially placed leaf scars. Outer 

 surface of cortex ornamented with very fine raised lines, which unite to form a fine 

 net-like reticulation. 



Remarks. — The genus is closely related to Bothrodendron, L. and H., but easily 

 distinguished by the net-like reticulation of the outer surface of the cortex and the form 

 of the leaf scars on the hitherto discovered species of the genus. 



Weiss describes two species — Pinakodendron musivum* and Pinakodendron 

 OhmanniA 



In Pinakodendron, musivum the leaf scars are oval-upright and placed in a slight 

 depression, which is surrounded on the lower margin by a slight ridge. The surface 

 ornamentation both above and below the leaf scars is very fine and faint, and the space 

 so occupied forms an elongated rhomboidal area, of which the centre is occupied by the 

 leaf scar. 



In Pinakodendron Ohmanni the leaf scar is of very peculiar form. It consists of 

 an upper transversely elongated triangular area, apparently not always clearly defined, 

 with two or three cicatricules placed immediately above a transverse ridge which 

 separates this upper portion from the lower triangular shield-shaped part, which has a 

 small circular depression at its basal extremity. I am inclined to regard the lower shield- 

 shaped portion the leaf scar proper, and that the cicatricules above this are probably so- 

 called ligule pits Unless this be the explanation of the structure, the leaf scar is other- 



* I.e., p. 61, pi. iii. figs. 16, 16a. 

 t I.e., p. 62, pi. iii. figs. 17, 17a, 18, 18a. 

 TRANS. ROY. SOC. EDIN., VOL. XL. PART IV. (NO. 31). 6 c 





