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 preceding. 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 j 

 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, Pterygotus, 

 Slimonia, Stylonurus, and Crossopterus ; and those in the 

 lower Coal Measures to Eurypterus (the Eidothea of Scoular), 

 which had yet been found only in the lower limestones of 

 Bathgate and Burntisland. 



