116 NEW YORK STATE MUSEUM 
Stylonurus myops 
Nepionic and neanic stages [pl. 51, fig. 1-13] 
1 Larger carapace 
Broad, flat border of carapace 
Distinct glabella 
Larger eyes (very large ocular nodes) 
Eyes nearer to margin 
Segments not differentiated 
Smaller number of segments 
Smaller telson 
No distinct ornamentation 
0 com” Aon HB W ND 
These lists of ontogenetic characters permit the following general 
inferences: | 
1 The carapace ts relatively larger in the larval stages; often very much 
so. This is especially marked in the representatives of Pterygotus, 
Hughmilleria and Stylonurus. It is also recognizable in the young of 
E.remipes; the few young specimens of E. lacustris are also 
suggestive of a larger size of the carapace but not conclusively so, since 
the preabdomen of the specimens-is probably accidentally contracted. In 
E. maria the carapace is distinctly shorter and wider than in the 
mature stage. This is in accordance with the entire character of this larval 
stage which in its broad carapace and broad short preabdomen, anterior 
divergent eyes and rapid contraction of the preabdomen distinctly exhibits 
the characters of the genus Eusarcus. The young carapace of E. scor- . 
pionis indicates no relatively larger size although the single individual 
available may be alrcady too far advanced to still exhibit this difference 
in Size. 
The shieldlike character of the carapace is sometimes still empha- 
sized by a broad flat margin, as in Stylonurus and Eusarcus (2) 
cicerops. 
2 The compound eyes are relatively much larger than in the mature 
stage; and sometimes borne on more prominent ocular nodes. The larger 
