from the Coal-measures of Illinois. 27 
had he seen a specimen showing a side view of even a few seg- 
ments of the animal. At any rate, our fossil is entirely dis- 
tinct, in all respects, from the typical species of Arthropleura 
of Jordan and von Meyer, which is almost certainly a Crus- 
tacean. 
Supplementary Note on some of the Morris Crustacea, &c., 
= formerly described. 
A number of additional specimens now before us, in various 
' conditions of preservation, of some of the articulates already 
described and figured in the Illinois State Geological Report, 
from the Grundy county locality, enable us to add some facts 
in regard to these fossils not determinable from the specimens 
first obtained. This additional information we give below :— 
fo) 
ing with the thoracic legs spread out on each side for walking, 
led us to think the former probably their natural posture, and 
show that the animal could probably stand and walk upon 
them, and that this may have been its natural attitude. It is 
worthy of note, that in all these specimens, the thoracic 
legs are all directed forward, and not a part of them forward 
and a part backward, as in most of the Amphipoda. 
These specimens also clearly show that the last joint of each 
