29 
culiar in its configuration-—he describes this 
inferior surface as being formed by the ante¬ 
rior part of the buckler being reflected beneath 
the animal so as to form a flat horizontal plane, 
which terminates in a kind of lunate spine, 
the horns of the crescent being curved towards 
each other. These horns are six lines in 
length, and their points are sharp and trans¬ 
lucent. We have received from Dr. Warder 
a specimen of this singular structure, which 
was found, with other fragments of the isote- 
lus, near Springfield in Ohio. Though it lies 
on the rock, unaccompanied by any other 
fragment of the animal, its exact resemblance 
to the figure given by Dr. Dekay leaves no 
doubt that it once belonged to an isotelus. 
Among other conjectures respecting the uses 
of this crescent-shaped structure, it is observed 
that when the animal was attacked “ it may 
roll itself up into a ball, as indeed it is often 
found, and by some mechanism these pro¬ 
cesses may be inserted into the corresponding 
cavities in the tail, and thus retain perma¬ 
nently a rolled position, presenting nothing 
