On the Occurrence of Arthrostigma gracile. LU9 
than an inch, but on that difference alone one is quite 
unwarranted in founding a new species. I am, therefore, 
led to conclude that the Perthshire specimens must be 
identified as Arthrostigma gracile, Dawson, and though they 
seem to be somewhat larger than the original specimens of 
the species, they do not appear to differ in any important 
character, as far as can be observed (from the material at our 
disposal), from the Canadian species. 
ARTHROSTIGMA GRACILE, Dawson. 
[Plate IIT.] 
Arthrostigma gracile, Dawson, Geol. Survey of Canada—The Fossil 
Plants of the Devonian and Upper Silurian Formations of 
Canada, 1871, p. 41, pl. xili.; part ii, 1882, p. 104, pl. xxiv., 
fig. 22. 
Description of specimens here figured :— 
Fic, 1.—This is the specimen given by Messrs Jack and 
Etheridge in their paper on p. 217, fig. 1. My figure is 
natural size. 
The fossil shows portion of a stem about 64 inches long, 
and rather under an inch broad at its thickest part. The 
arrangement of the leaves is not clearly shown, but the 
stem exhibits the irregular longitudinal striations and the 
spine-like leaves projecting past the margin of the stem. 
These, when perfect, are here seen to be fulcate. 
In the description of the reduced figure given by the 
authors already mentioned, they say, “portion of a simple 
stem, with the cellular tissue destroyed at one end, leaving 
the vascular axis.” There is evidently some mistake in this 
description, for at no part does the specimen show any trace 
of the vascular axis, unless it be found in indications of 
a ribbon-like band running up the centre of the stem! 
1Qn another specimen from the quarry west of Braeandam House (Reg. 
No. M/482>), among other fragments of stems is one three inches long and 
rather over an inch wide. It narrows slightly towards one end, and up its 
centre runs a clearly defined carbonaceous ribbon-like band, about one-tenth 
inch thick. This may be the remains of the vascular system shadowed 
through the much compressed stem, 
