THE EURYPTERIDA OF NEW YORK 169 
We add here several more photographs of parts of very young in- 
dividuals, among them a carapace [pl. 5, fig. 1] that is much smaller than 
any others before mentioned (2.5 mm long). This is especially re- 
markable for the great size and prominence of the compound eyes, as 
well as of the ocellar mound, a feature that was uniformly observed in the 
nepionic eurypterids from Otisville. The eyes are here 1 mm long, or four 
tenths the length of the carapace as against one fourth or 2.5 in the mature 
individual. This relatively great size of the eyes in youth is still apparent 
in larger individuals, as that figured in plate 4, figure 4. While these eyes 
of the young are relatively larger than those of the adult, they still remain 
entirely in the anterior half of the carapace, thereby producing an appearance 
of more anterior position which, however, in the figure cited from Zittel- 
Eastman is somewhat exaggerated. 
The outline of the carapace in the youngest specimen is still rounded 
at the antelateral corner, but soon becomes squarish as in the older ones 
[pl. 5, fig. 1, 2]. The carapace itself is distinctly larger in comparison to the 
whole body than in the ephebic stage, although on account of the distortion 
of one or another part of the body in every observed individual it is diffi- 
cult to demonstrate this fact by measurements. In specimen plate 4, 
figure 1, the smallest whole individual observed, the carapace occupies fully 
one fourth of the whole body, while in the larger specimens it is less than 
one fifth the length of the body. 
The swimming leg when reflexed will reach to the tenth segment 
or farther in young individuals [pl. 4, fig. 1-3], while in the ephebic stage it 
reaches only to the seventh segment. The posterior endognathites appear 
also to be slightly longer. 
It is questionable whether the preabdomen is relatively shorter in 
the young at our disposal than in the adult although the Otisville material 
indicates that in the nepionic stage the preabdomen may well have been 
shorter and more abruptly contracted toward the postabdomen. In the 
specimens before us, however [pl. 4, fig. 1-3], the relatively greater size 
of the carapace produces the impression of a relatively smaller and shorter 
