Page:The Eurypterida of New York Volume 1.pdf/118

 those of  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 obtained at Buffalo and Jerusalem hill youthful stages of,  ,   and   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 considered as ontogenetic characters of larger scope. We here briefly summarize these general ontogenetic features from lists of specific ontogenetic characters taken from the detailed descriptions of the development given under the respective species.

The neanic stage is distinguished from the mature by
 * 1) Larger, less quadratic carapace
 * 2) Larger, more anteriorly situated compound eyes
 * 3) Larger and more prominent ocellar mound
 * 4) Larger swimming feet
 * 5) Possibly a more compact, more rapidly contracting preabdomen

Neanic stage [ pl. 11, fig. 1]
 * 1) Larger size of compound eyes
 * 2) Possibly more compact form of preabdomen

Nepionic and neanic stages [ pl. 21, fig. 1–11]
 * 1) Excessively short and wide, subtriangular carapace
 * 2) Very large, anteriorly situated diverging compound eyes
 * 3) Rapid contraction of abdomen
 * 4) Short, wide preabdominal segments
 * 5) Larger swimming feet