304 NEW YORK STATE MUSEUM 
Ontogeny of Stylonurus myops 
Among the early stages of eurypterids obtained at Otisville is a num- 
ber of very minute individuals, that are noticeable for their owllike 
appearance due to the very broad, anteriorly emarginate carapace and 
their immense hemispherical and disklike eyes [pl. 51, figs. 1-6]. Al- 
though there is a considerable gap in size in the series of these speci- 
mens and of the smallest of the carapaces [pl. 51, figs. 7-9] which undoubtedly 
belong to S. myops, these small entire individuals seem properly ~ 
referred here, for the following reasons: The form of the carapace is 
clearly that of S. myops which is the only one in the Otisville fauna 
possessing a subrectangular outline; the position of the eyes corresponds 
to that found in the adult stages of 5S. myops; the broad rim of the 
carapace, a characteristic feature of S. myops and not observed in 
other members of this fauna, is present in these young individuals. 
In surveying this whole series, one distinguishes three ontogenetic 
groups, the first represented by the small entire individuals on plate 51, 
figures 1-6; the second by the group plate 51, figures 7-14, and the last 
by the specimens plate 52, figures 1-4, 10. As the smallest specimens 
of the first group are but little larger than the eggs of Limulus and are 
thoroughly larval in their character, we consider them as representing the 
nepionic’ stage. The next group which is intermediate in its character 
between the first and last may be considered as representing the neanic 
growth stage, since the last group belongs to specimens of ephebic or ma- 
ture age, as far as we can judge, although we suspect that these are only 
the earliest ephebic substage. | 
The nepionic stage is again subdivisible as far as our material is con- 
cerned, into two substages. The first of these, illustrated by the figures 
1-3, [plate 51] is characterized by (1) the relatively large size of the cara- 
pace to the body (proportion as 1 : 3.75 in the former and as 1: 5 in the. 
latter); (2) the evenly terete or conical form of the body which makes the 
carapace also the broadest part of the integument; (3) the presence of a dis- 
tinct border surrounding the whole carapace; (4) the immense size of the 
