27 
the under side of which we have not yet dis¬ 
covered, was probably furnished below, on 
each side of the abdominal cavity, with or¬ 
gans, which performed the double office of 
feet and lungs. Now, as our fragments de- 
velope all the inferior surface except the por¬ 
tion beneath these five articulations of the 
abdomen, it is probable that our trilobite was 
a decapodous animal . Professor Brongniart 
long ago imagined, that the reason why no 
traces of these organs have yet been discover¬ 
ed, is that the trilobites held that place among 
crustaceous animals in which the antennae 
disappear, and the legs become transformed 
into soft paddies incapable of preservation. If 
this supposition be true, we shall in vain look 
for any further discoveries below the upper 
shell of the trilobite. What affords, we think, 
increasing probability to the opinion we have 
just advanced, with regard to the situation of 
the abdominal cavity, and the organs of loco¬ 
motion below the five abdominal arches above 
mentioned, is, that when the animal rolled it¬ 
self up for protection, this portion of the body 
