= FOSSIL FORMS 279 
In WNeolimulus, Belinurus, and Prestwichia, lateral eyes are 
present on the sides of the axial parts of the carapace, and near 
its frout margin median eyes have been found in the two last- 
named genera. , 
In nearly all the specimens of Palaeozoic Xiphosura! which 
have been found nothing is seen but the dorsal surface of the 
body; im only a very few cases have any traces of the append- 
2 
ages been seen, but, so far as known, they appear to have the 
same general character as in Limulus. 
Aglaspis, found in the Upper Cambrian of Wisconsin, has 
been regarded as a Xiphosuran. If that view of its position is 
correct, then Aglaspis will be the earliest representative of the 
group at present known. Other genera of Palaeozoic Xiphosura 
are Bunodes, Bunodella, and Pseudonisevs in the Silurian ; Pro- 
tolimulus in the Upper Devonian; and Prolimulus in the 
Permian. 
! The British fossil forms of this group are described and figured by H. Wood- 
ward, ‘‘ Monograph of the Merostomata,” Palacontogr. Soc. 1866-78, and Geol. 
Mag. 1907, p. 539. 
2 Packard, ‘‘Carb. Xiphos. N. America,” Mem. Nat. Acad. Sct. Washington, 
lii., 1885, p. 146, pl. vi. fig. la, pl. v. fig. 3a (restoration). Williams, Amer. 
Journ. Sct. (3), xxx., 1885, p. 45. Fritsch, Fawna d. Gaskohle, iv., 1901, p. 64, 
pl. 155, figs. 1-3, and text-figures, 369, 370. 
