364 -_ NEW YORK STATE MUSEUM 
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 sur- 
passes the ultimate segment in length and in width by one third. The 
character of the marginal serrations is asin P. macrophthal- 
mus; and as in the latter, the telson possessed a median axis or thick- 
ening 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 pre- 
served 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 seg- 
ment is subcylindrical, about eight times as long as wide in the compressed 
state; contracted in the basal seventh of its length, and very gradually ex- 
panding 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 verti- 
cally. 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 
