5 
pected the softer portions would leave any 
traces whatever in the rocks which have so 
perfectly preserved other portions of these 
ancient inhabitants of our planet; for these 
reasons, and some others which we shall pre¬ 
sently mention, the legs of the trilobite have 
been supposed to be soft and very perishable 
paddles. 
Though much controversy formerly existed 
as to the true nature of the trilobite, it is 
now admitted by all naturalists to occupy a 
place among crustaceous animals. The ex¬ 
isting genera to which they are most analo¬ 
gous in their general structure are the serolis, 
the limulus, and the branchipus. In our 
monograph we announced the discovery of a 
recent trilobite in the southern seas, near the 
Falkland islands: this proves to be a species 
of the genus serolis established by Dr. Leach. 
In the configuration of its upper shell it ap¬ 
proaches exceedingly near to that of some of 
the trilobites; the chief difference between 
the recent and fossil animal consists in the 
crustaceous legs and antennae of the serolis. 
1 * 
