On the Occurrence of Arthrostigma gracile. 107 
given here, and what is said refers more to its condition of 
preservation. 
“ An Orkney specimen, lately sent me by Mr Wm. Watt, 
from a quarry at Skaill, has much the appearance of one of 
the smaller ferns, such as the moorworts, sea spleenworts, or 
maidenhairs.” 
“Tt exists as an impression in diluted black, on a ground of 
dark grey, and has so little sharpness of outline, that, like 
minute figures in oil paintings, it seems more distinct when 
viewed at arm’s length than when microscopically examined, 
but enough remains to show that it must have been a 
terrestrial, not a marine plant. The accompanying print 
(fig. 56) may be regarded as no unfaithful representation of 
this unique fossil in its state of imperfect keeping.” 
This interesting specimen is now preserved in the Palzeon- 
tological Collection of the Museum of Science and Art, 
Edinburgh. As pointed out by Hugh Miller, it is very 
imperfectly preserved, but seems to me to very much 
resemble the fruit of Arthrostigma—it is evidently not a 
fern—but its true nature cannot, on account of its imper- 
fect preservation, be satisfactorily determined. Arthrostigma 
has not, however, as far as I am aware, been yet met with in 
Orkney, but the Old Red Sandstone plants have been so 
little collected systematically, that one can scarcely say what 
species do or do not occur at most of the localities from which 
plant remains have been secured. 
Having now so fully discussed the broader questions 
referring to the genus Arthrostigma, we may turn our 
attention to the Perthshire examples which are the 
immediate cause of this communication. 
Of these there are five examples before me. They consist 
of fragments of stems, varying in length, and of a width 
from rather under # of an inch to 1} inch. They are much 
compressed, and show projecting from their margins the 
spine-like rudimentary leaves. These are generally slightly 
falcate or hook-shaped, though occasionally straight. When 
the leaves are removed from the stems, they leave behind a 
circular scar; this, however, is seldom well shown on our 
specimens, though in a few instances it.is exhibited. I do 
