26 
most the whole of the inferior surface, except 
the portion which lies below the five articu¬ 
lations of the back commencing with the 
fifth from the buckler or shield; what we 
shall offer in regard to this portion of the 
animal must be merely hypothetical, or found¬ 
ed on certain analogies of structure which 
probably existed between living crustaceous 
animals and the fossil remains of such as in¬ 
habited the most ancient seas. 
Some of our fragments, we think, exhibit a 
transverse section of our trilobite, showing 
the position and figure of the abdominal 
cavity which once contained a portion of the 
viscera of the animal. One of the sections is 
through and parallel with the sixth articu¬ 
lation of the back: by this means we have 
discovered that some of the viscera were placed 
in a cylindrical cavity running beneath the 
vertebral column, and that the side lobes 
were only a covering and protection to the 
soft paddles or feet placed below, as may be 
seen in a similar structure in the serolis. 
Each of the five articulations of the abdomen, 
