II4 NEW YORK STATE MUSEUM 
those of Eurypterus lacustris and Pterygotus that they may 
be safely considered as representing the first larval or nepionic stage. Our 
large amount of material has allowed us to connect these larval stages with 
the adult forms by a fairly continuous series. There have also been ob- 
tained at Buffalo and Jerusalem hill youthful stages of Eurypterus 
remipes, E.lacustris, Pterygotus macrophthalmus 
and Eusarcus scorpionis which present characters indicating 
their neanic condition. 
All these young individuals have a number of characters in common 
which distinguish them from the adults and for this reason may be con- 
sidered as ontogenetic characters of larger scope. We here briefly sum- 
marize these general ontogenetic features from lists of specific onto- 
genetic characters taken from the detailed descriptions of the development 
given under the respective species. 
Eurypterus remipes [pi. 4, fig. 1-4; pl. 5, fig. 1, 2] 
The neanic stage is distinguished from the mature by 
1 Larger, less quadratic carapace 
Larger, more anteriorly situated compound eyes 
Larger and more prominent ocellar mound 
Larger swimming feet 
Possibly a more compact, more rapidly contracting preabdomen 
mm B&B Ww bd 
E. lacustris 
Neanic stage [pl. 11, fig. 1] 
1 Larger size of compound eyes 
2 Possibly more compact form of preabdomen 
E. maria 
Nepionic and neanic stages [pl. 21, fig. 1-11] 
Excessively short and wide, subtriangular carapace 
Very large, anteriorly situated diverging compound eyes 
Rapid contraction of abdomen 
Short, wide preabdominal segments 
Larger swimming feet 
mn BB GW HO #4 
