430 NEW YORK STATE MUSEUM 
and the telson is in both specimens narrower than in P. macroph- 
thalmus, a difference which is surely in part and perhaps wholly due 
to preservation, the thin telsons being somewhat laterally compressed. 
On account of the scarcity of the material we do not know to what 
extent these differences are expressions of different growth stages, but 
it is quite obvious that P. cobbi as represented by these specimens, 
was remarkably similar in all its features, save the pincers, to P. buf - 
“faloensis and PF) m2 ¢movp iti e lair: 
Judging from the fragmentary pincers of the specimen figured by 
Pohlman [1883, pl. 3, fig. 3] as P. buffaloensis, we surmise that 
this also belongs to P. cobbi. 
Horizon and locality. Bertie waterlime, Schooley’s farm, Litchfield, 
Herkimer co., N. Y. ; 
121 
Fig. 120-21 Pterygotus cobbi var. juvenis nov. 
Fig. 120 Dorsal aspect. Fig. 121 Ventral aspect. Both 
somewhat laterally compressed. Natural size 
