4 
formation. Dr. Buckland remarks, “ No 
trilobites have yet been found in any strata 
more recent than the carboniferous series; 
and no other crustaceans, except three forms 
which are also entomostracous, have been 
noticed in strata coeval with any of those that 
contain the remains of trilobites; so that dur¬ 
ing the long periods that intervened between 
the deposition of the earliest fossilliferous 
strata and the termination of the coal forma¬ 
tion, the trilobites appear to have been the 
chief representatives of a class which was 
largely multiplied into other orders and fami¬ 
lies after these earliest forms became extinct.” 
From the multitude of trilobites and frag¬ 
ments of trilobites which have been discover¬ 
ed in different parts of the world, most of 
which present nothing but portions of the 
upper shell of the fossil, the under side, of 
the animal, and the form and arrangement of 
the organs of locomotion, seemed an almost 
hopeless discovery. As the solid parts of the 
animal structure alone are for the most part 
susceptible of petrifaction* it is not to be ex- 
* 
