line of the dorsal side is likewise marked, in the middle third of its length, by a keel and covering of massive scales.
The telson is very broadly obovate to circular in outline. It surpasses the ultimate segment in length and in width by one third. The character of the marginal serrations is as in P. macrophthalmus; and as in the latter, the telson possessed a median axis or thickening which here is equipped on the dorsal side, with large spines [pl. 73, fig. 2].
Appendages. The form of the epistoma could not be made out in this species.
Some of the preoral appendages or chelicerae are so admirably preserved as to shed light on the structure of these organs and to decide the much disputed number of their segments and the character of the basal attachment. These appendages were long and very powerful, their length equaling fully one half that of the body without the telson. The first segment is subcylindrical, about eight times as long as wide in the compressed state; contracted in the basal seventh of its length, and very gradually expanding toward the distal end. The next segment, which with the third forms the vicious looking pincers or chelae, is of about equal length with the first and easily revolved on it with a rounded basal articulating surface. The basal third of the second segment is inflated, evidently to receive the strong muscles operating the free ramus. Both rami are nearly straight or slightly convex outward, tapering toward the tip and relatively slender. Their distal parts are not roundly curved as in P. cobbi and the British species, P. anglicus and bilobus, but end in a sharp distal point and each carries a terminal tooth directed slightly inward, resembling in this structure the jaws of P. osiliensis. The fixed ramus carries on the proximal half an irregular series of teeth directed obliquely forward, and on the distal half, smaller teeth that stand vertically. One or several of the oblique teeth surpass all others in length and extend daggerlike into the cavity between the jaws. They are finely barbed on the inner margin, a feature not observed in any congeneric
