108 Dr, Dawson on an Erect Sigillaria 



part the ribs are very prominent, and there are twenty-six in the 

 whole circumference, the breadth of each rib being about nine- 

 tenths of an inch. On the outer or cortical surface each rib is 

 flattened, or even concave, along the middle, and strongly round- 

 ed at the sides, descending into deep intercostal furrows ; the flat 

 mesial portion being smooth, the lateral portions marked with 

 sharp vertical ridges, and in places with very delicate longitudinal 

 and transverse striae. The leaf-scars extend across the smooth 

 middle portion of the rib, and are distant from each other one 

 inch vertically. In form they resemble those of Sigillaria trans- 

 versalis, S. Defrancii," and S. Brochantii, Brongt., being trans- 

 versely lanceolate, emarginate above, with acute lateral edges. 

 Those best diplayed show two vascular punctures, with a third 

 mark or prominence between and rather below them. On the 

 so-called ligneous surface, or that of the inner bark, the ribs are 

 slightly furrowed or striated lengthwise ; and the leaf-scars are re- 

 presented by two deep punctures of the vascular scars. (Fig. 2.) 



In tracing the ribs downward, some of them wedge out and dis- 

 appear : so that at the middle of the length of the trunk there 

 may be about 22 ; each with a breadth increased to one inch and 

 four-tenths, and flatter than those at the top, with the intercostal 

 furrow shallower. The leaf-scars are now widened transversely, 

 aud have lost their minute markings on the cortical surface ; 

 while on the ligneous surface the vascular punctures are twice as 

 far apart as at the top. About the middle the vertical distance of 

 the scars diminishes somewhat suddenly to seven-tenths of an 

 inch. 



In the lower third of the stem the ribs are quite obliterated, 

 and the whole surface is wrinkled with coarse waving striae or 

 small furrows, due apparently to the expansion of the outer bark. 

 The leaf-scars still remain in regular vertical rows ; but these are 

 reduced to about twelve, and apparently at the base to as few as 

 nine. The vertical distance of the scars is still about 0*7 inch ; 

 but the transverse distance between the centres of the rows is in- 

 creased to 2-8 inches or more. In form the leaf-scars are now 

 transverse furrows, an inch or more in length, and the 

 vascular punctures are half an inch or more apart in each 

 scar. A single row of these wider scars is shown in (Fig. 3.) 



Of the roots I could obtain no specimens ; but the markings on 

 the bark at the base of the trunk are precisely similar to those on 

 many Stigmarian roots found attached to less perfectly preserved 



