THE EURYPTERIDA OF NEW YORK 349 
Laurie discovered the epicoxite and the second (female) form of the 
opercular appendage. The New York rocks furnished to Hall only 
fragments of the genus on which he based three species, P. cobbi, 
P macrophthalmus and P. osborni. The waterlime 
quarries at Buffalo have since afforded somewhat more extensive series 
of these remains, some of the specimens excellently preserved. Grote 
and Pitt [1877] and Pohlman [1881-86] made use of some of these, 
basing thereon descriptions of six alleged species, all of which have proved 
to belong to two forms, Hall’s P. cobbi anda new type, here recognized 
as P. buffaloensis (Pohlman). A fossil from the same locality 
described by Pohlman as a Ceratiocaris, is the telson of a gigantic 
~Pterygotus. (P. grandis). Finally the Pittsford shale, the dark 
shale of the Shawangunk grit, and the Frankfort shale, have furnished 
representatives of other species, viz, P. monroensis, P. globi- 
ceps, P. prolificus and P. nasutus, allof them as yet very 
incomplete. As Hall’s species P. osborni has proved to be a synonym 
of hs P. macrophthalmus, there remain out of the considerable 
number of proposed speciesof Pterygotus from the New York rocks, only eight 
whose differentials can now be regarded as satisfactorily determined, viz. 
P. macrophthalmus Hall P. grandis (Pohlman) 
P. cobbi Hall P. monroensis Sarle 
P. buffaloensis (Pohlman) Clarke & Ruedemann P. prolificus nov. 
P. globiceps nov. P, nasutus nov. 
On this continent no Pterygoti have been found outside of New York 
and only two of the New York species (P. macrophthalmus and 
P. buffaloensis) are known in entire specimens, all the others 
being based on carapaces, chelae or telsons. The material of these two 
species, however, is so complete that it has allowed a detailed description 
of the forms and some additions to our knowledge of the structure of 
the genus. Among these is the demonstration of the identity of the 
structure of the ‘chelate antennae’”’ of Pterygotus with the chelicerae 
of Eurypterus and their composition of but three segments (as already 
suggested by Laurie) instead of eight as formerly assumed; the demon- 
»? 
