fragment of a segment [pl. 53, fig. 13] exhibits a curiously serrated posterior margin. This recalls the frontal serrations of the carapace of S. cestrotus, but the segments of that species have not shown this structure, although on account of their rather poor preservation, this does not yet demonstrate the absence of this fringe. We are not certain that this specimen is referable to Stylonurus.
To a gigantic Stylonurus or Pterygotus probably should also be referred two fragments of plates with marginal rows of slightly curved, rather blunt spines [pl. 53, fig. 16, 17]. These are apparently portions of the manducatory edges of coxal segments. In the smaller specimen the teeth are very thick and solid, in the second they are so much wrinkled and shrunken that they give the impression of having been hollow processes. It is possible that these remains require an entirely different explanation, but the material is at present too fragmentary to permit of positive conclusions. There is a suggestion of similarity between these peculiar fringed bodies and the supposed combs of giant scorpions such as have been described by Peach as Glyptoscorpius, both the fringe and the parallel lines of the base of the fragments indicating the structure seen in the rhachis and the comb of certain recent scorpions. With present knowledge the comparison can be carried no further.
Subgenus DREPANOPTERUS Laurie
In 1892 Laurie created a new genus for a single, then rather incompletely known eurypterid, from the Siluric rocks of the Pentland hills in Scotland. He defines the genus as follows:
Carapace broader than long; widest about two fifths from anterior margin. Body, 1st segment wider than posterior margin of carapace; increases in width to 3d segment, and then tapers rapidly. Limb elongated, subcylindrical, terminating in a very slightly expanded joint, concave on posterior margin.
The subsequent discovery of two other species and of better specimens of the genotype led Laurie [1899, p. 582] to consider the point of chief generic importance to be a negative one: "Last pair of appendages
