THE EURYPTERIDA OF NEW YORK 333 
them strong evidence of the closer relationship of Hughmilleria to Ptery- 
gotus; for it is obvious that the appendage in P. anglicus and 
P. osiliensis is only a more extreme development of that of Hugh- 
milleria by the expansion of the distal end. As a last character suggesting 
Pterygotus the small distal expansion of the swimming legs is cited. 
Considering the wide variation in this character within the genus Eurypterus 
(compare for instance the swimming legs of Eurypterus remipes 
and E. kokomoensis), this similarity with Pterygotus is of but 
little import. 
As characters distinctive from Pterygotus, Sarle cites the preoral 
appendages, the spiniform walking legs and the telson. The difference in 
the preoral appendages is described as follows: 
These are stout, three jointed, chelate organs, so short that when 
extended they barely equal one half the length of the cephalothoracic 
shield. The pincers are edentulous and bevel-edged and in their normal 
position lie folded over the basal joints so that their tips converge close 
to the anterior border of the mouth. Extended, these organs project beyond 
the border of the shield for perhaps half their length; when turned straight 
back, their tips lap over the end of the metastoma. In Pterygotus, on 
the contrary, these organs are very long, having, at least in Pt. bi- 
lobus Salterand Pt. macrophthalmus Hall a length fully one 
third that of the entire animal; and consist of ponderous, dentate pincers 
supported on a slender, retrally tapering proximal joint of such a length 
as must necessarily have prevented the pincers being used at the mouth, 
unless these appendages were somewhat retractile, as suggested by Laurie. 
Though the preoral appendages of Hughmilleria are larger than those 
of Eurypterus they differ still more widely from the very long appendages 
of Pterygotus with their dentate pincers, but they may well be considered 
as indicating a tendency to a development of Pterygotuslike chelicerae. 
The difference between Pterygotus and Hughmilleria in the character 
of the spiniform legs, is clearly set forth by Sarle! and the slender lance- 
olate telson is distinctly a Eurypteruslike feature. / 
‘The next important difference is in the character of the spiniform walking legs. 
_ As in Pterygotus, these consist of seven joints, but the several pairs present 2 greater 
