ARTHROPODA 
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Permian. 
Carboniferous. 
Devonian. 
Silurian. 
Ordovician. 
Cambrian. 
Pre-Cambrian. 
. 
SUB-KINGDOM VII | 
TRILOBITA. 

TABLE SHOWING VERTICAL RANGE OF TRILOBITES. 
Families. 
Cambrian. 
Ordovician. 

Devonian. 
Carboniferous. 
Permian. 
Silurian. 

Order 1. Hypoparia 
Family 1. Agnostidae 
2. Harpedidae 
3. Trinucleidae . 
Order 2. Opisthoparia 
Family 1. Conocoryphidae 
2. Olenidae 
3. Asaphidae 
1, Proétidae 
5. Bronteidae 
6. Lichadidae 
7. Acidaspidae 
Order 3. Proparia 
Family 1. Encrinuridae. 
2. Calymmenidae 
3. Cheiruridae 
4. Phacopidae 
Total Number of Families 

| Sie) lil 8 1 1 
[The foregoing chapter on the Trilobita has been abbreviated from an essay prepared 
expressly for this work by our foremost authority on the group, Professor Charles E. Beecher 
] \ h A g 
of Yale University, New Haven. 
the text, borrowed mainly from Dr. Beecher’s original contributions. 
About a score of new figures have also been introduced in 
These last should be 
consulted by every student in connection with the present chapter.—TRANs. ] 
