354 NEW YORK STATE MUSEUM 
The swimming legs are small as in all Pterygoti; when turned back 
they do not reach the anterior margin of the fourth tergite.. 
The gnathobase is like that of P. buffaloensis; and it prob- 
ably possessed a like relation in size to the swimming leg and carapace. 
In regard to the other joints of the swimming leg, we may also refer 
to the full description of these parts in the larger species from Buffalo, 
there being no specific differences apparent in these organs. 
The ‘etastoma is elongate cordate; its greatest width, which is a little 
bevond the middle, is about one half the length. The anterior margin 
is deeply emarginate, the posterior part contracted and the posterior 
end somewhat acutely rounded. | 
The endostoma has not been observed [see P. buffaloensis]. 
The opercular appendages have not been preserved favorably in any 
of our specimens. The type of P. osborni [pl. 71, fig. 6] retains 
only the posterior portion of the operculum, together with the correspond- 
ing part of the opercular appendage, which indicates a short subtriangular 
organ that would correspond to the appendage of the male of other euryp- 
terids. Near the broken edge the margin of an emarginate lobe is exposed 
and the posterior angle bears two dark spots suggestive of pores. The 
opercular apperidage of the female has not been observed by us in this 
Species. 
The ornamentation agrees with that here described of P. buffalo- 
ensis. . 
Measurements. The few fairly complete specimens at our disposal 
are immature individuals. The specimen on plate 69, figure 2 gives the fol- 
lowing measurements: : 
Length of carapace about 25 mm 
Width, about 35 mm 
Length of largest tergite, 11.5 mm 
Width, 44.5 mm 
Length of first postabdominal segment, 11 mm 
Width, 39 mm 
