THE EURYPTERIDA OF NEW YORK 189 
selected. These specimens differ from the mature stage in the following 
characters: 
1 The carapace is still relatively wider though not as wide as in the 
preceding stage and already approaches a semicircular shape. 
2 The compound eyes are still relatively large, holding a median 
position in proportions between the nepionic and ephebic stages. In 
plate 21, figure g the length of the eyes to the length of the carapace 
is as 3:7, while in the nepionic stage they are as 3:6 and those of 
the ephebic stage as 3:9. They are also distinctly nearer to the frontal 
margin than in the mature specimens and the ocular nodes are more 
prominent than in later stages. They still show a distinct tendency to 
converge forward. The crescent visual surface is now distinctly seen, but 
it appears still broader than in the mature stage. 
In many examples of this stage the ocellar mound is so large and 
distinct that its greater size and prominence in more youthful stages may 
be legitimately inferred [figs. 3, 4, 8, ro]. | 
The abdomen in these neanic specimens is already as slender as in the. 
adults [fig. 8]. One exception is the fine specimen [pl. 22, fig. 7], which is 
a little broader than the others. The presence of the lobes of the post- 
lateral angles, however, indicates that this individual was flattened out 
before burial. —— 
Measurements. Length of smallest nepionic individual, 5.25 mm; its 
width, 2mm; width and length of carapace, 2 mm and 1.1 mm; length 
of compound eye, .45 mm; length of swimming foot, 1.6 mm. 
An average specimen [pl. 21, fig. 12] measures in length (with the 
telson gone) 63 mm; its greatest width, 16 mm; the length of its cara- 
pace is 12 mm; that of the first segment 1.5 mm and that of the third 
3.5 mm. The last segment is 6.5 mm long and 6 mm wide. 
The largest carapace observed measures but 16 x 11 mm, so that this 
form is one of the small species of the genus. a 
Position and localities. Abundant in the fossiliferous shale of the 
Shawangunk grit at Otisville, N. Y. 
