OBSCURE NATURE OF TRILOBITES. 391 
attracted attention, from their strange pecu- 
liarities of configuration. M. Brogniart, in his 
'valuable History of Trilobites, 1822, enumerated 
five genera,* and seventeen species; other writers 
(Dalman, Wahlenberg, Dekay, and Green,) have 
added five more genera, and extended the number 
af species to fifty- two ; examples of four of these 
Sonera are given in Plate 46. Fossils of this 
family were long confounded with Insects, under 
tfie name of Entomolithus paradoxus; after many 
disputes respecting their true nature, their place 
fias now been fixed in a separate section of the 
class Crustaceans, and although the entire family 
appears to have been annihilated at so early a 
period as the termination of the Carboniferous 
strata, they nevertheless present analogies of 
structure, which place them in near approxima- 
tion to the inhabitants of the existing seas.f 
The anterior segment of the Trilobites (PI. 46, 
a, passim,) is composed of a large semi-circular. 
Or crescent-shaped shield, succeeded by an ab- 
domen, or body (c), composed of numerous seg- 
‘ifients folding over each other, like those in a 
Lobster’s tail, and generally divided by two 
* The names of these Genera are Calymene, Asaphus, Ogyges, 
Taradoxus, and Agnostus. Some of these terms are devised ex- 
pressly to denote the obscure nature of the bodies to which they 
^re attached ; e. g. Asaphus, from a<ra<j>^Q, obscure ; Calymene, 
^rom K€Ka\vuutvri, concealed ; ^apado^oe, wonderful ; ayywaroc, 
unknown. 
t See M. Audouin’s Recherches siir les Rapports naturels qui 
«xistent entre les Trilobites et les Animaux articules. 
