232 Proceedings of the Royal Physical Society. 
beds" of Upper Lanarkshire, in 1857, by Dr Slimon of Les- 
mahagow, and was a smaller and more slender species than 
the precediDg. It had the same general aspect, but had the 
carapace more quadrate, the eyes less central, and the two 
first pairs of limbs armed with spines at the joints, hence 
the name which Mr Page had given it in 1858. Fragments 
of S. Powriei had been found in the lowermost Old Eed 
of Lanark ; but in these, as in the Forfar specimens, the 
characters were distinct from those of S. spinipes, as might 
be seen from the casts now before the Society. The third 
species, S. armatus (see Plate III.), had been obtained by 
Mr Powrie from the Forfar flagstones in 1863, and was dis- 
tinguished from the two preceding by its greater size, shorter 
carapace, shorter and broader swimming limbs, and by the 
bold lateral processes (epimeral processes?) of its abdominal 
segments, from which the name armatus had been suggested. 
The length of this specimen, when entire, as might be seen 
from the cast, was 3 feet 6 inches, but, though exceeding 
the other species in this respect, it fell far short of species 
of Pterygoti from the same formation. 
The beautiful casts and drawings before the Society, and 
the account Mr Page had formerly given of the Eurypterite 
family, rendered further description on this occasion un- 
necessary. He had seen fragments both from the Lanark 
and Pentland Passage-beds and the Forfar Old Eed, which 
appeared to belong to other species of Stylonurus ; but as 
sculpturing, size, and form of appendages, might be indi- 
cative of age or of sex, as well as of species, he thought it 
unwise to cumber the science with doubtful and provisional 
species, and contented himself, in the meantime, with merely 
noting the fact of the occurrence of these fragments, which 
consisted of detached limbs, abdominal segments, and tail- 
plates. So far as was known at present, the Eurypterites 
occurring in the upper Silurian and lower Old Eed of Scot- 
land were restricted to the genera Eurypterus^ PterygotuSy 
Slimonictf Stylonurus, and Grossopterus ; and those in the 
lower Coal Measures to Eurypterus (the Eidothea of Secular), 
which had yet been found only in the lower limestones of 
Bathgate and Burntisland. 
