THE EURYPTERIDA OF NEW YORK Ig5 
types of E. eriensis came from the hydraulic limestones (Monroe 
formation) of Beach Point, Put-in-Bay Island, Lake Erie. 
Remarks. E. microphthalmus is well characterized by a 
number of peculiarities, the most notable of which are the round outline 
of the head, the small size and subcentral position of the lateral eyes 
and the short compact form of the preabdomen, from which the cylindrical 
postabdomen is well set off. The slight compression of both the carapace 
and the abdomen shows that the integument must have been relatively 
very strong. To this fact may be also due the absence of the scales on the 
surface. 
While the differences between the carapaces of E. microphthal- 
mus and E. eriensis, cited by the author of the latter species, 
seemed well founded as long as. the poorly preserved type of the former 
species or the not quite successful representation of the same were solely 
available, the specimens which have lately been collected in the Manlius 
limestone, leave no doubt of the identity of the Ohio specimens with 
E.microphthalmus. The proportions of the carapaces are the 
same, within the small variation due to different compression and to the 
developmental changes. 
| E. microphthalmus is, stratigraphically considered, an iso- 
lated form, since it is the sole eurypterid hitherto known from the 
Manlius limestone. It is likewise isolated from the preceding eurypterids 
by the series of peculiar features cited above as characteristic of this form, 
and though the form is in general outline near enough to the preceding 
E.remipes so that its derivation from that common species could 
be conceived, the fact remains that it is more closely related to later species, 
like E. brewsteri Woodward, from the British Old Red sandstone, 
with which it has in common the round outline of the carapace, the 
small size, forward and approximate position of the eyes—that is, all the 
features which give it its characteristic aspect. The Old Red species 1S 
also without ornamentation of the carapace. A third species exhibiting 
the same characters, except the lack of ornamentation, is E. a pprox- 
