PLATE II 

 DEVELOPMENT AND CLASSIFICATION OF TRILOBITES 



Figures are approximately of the same size to facilitate comparison. 

 The dorsal areas of the free-cheeks are shaded. 



Ontogeny of Sao hirsuta Barrande (Pages 128, 129) 



Figure 1. — Protaspis stage. 



Figure 2. — Cephalon ; uepionic stage of individual having two free 

 thoracic segments. 



Figure 3. — Cephalon; later nepionic stage of individual having eight 

 free tlioracic segments. 



Figure 4. — Cephalon of adult. (Figures 1-4, after Barrande.) 



Ontogeny of Dalmanites sociatis Barrande (Pages 128, 129) 



Figure 5. — Protaspis stage. 



Figure 6. — Cephalon ; nepionic stage of individual having three 

 free thoracic segments. 



Figure 7. — Cephalon; nepionic stage of individual having seven 

 free thoracic segments. 



Figure 8. — Cephalon of adult. (Figures 5-8, after Barrande.) 



Hypoparia (Pages 134-138) 



Figure 9. - Cephalon of Ac/nostus ) Agnostid^. 



Figure 10. — Cephalon oi Microdiscus ^ ° 



Figure 11. — Cephalon of //arpe.s J- HarpedidEe. 



Figure 12. -Cephalon of Trinucleus ? Trinucleid*. 



iiGUKE lo. — Cephalon of Ampyx ^ 



Opisthoparia (Pages 138-152) 



Figure 14. - Cephalon of Atops ? Conocoryphid^. 



Figure 15. — Cephalon ot Cnnocoryplie \ ■"^ 



Figure 16. — Cephalon of Ptychoparia \ Qienidse 



Figure 17. — Cephalon of Olenus J 

 Figure 18. - Cephalon of Amplius Asaphidje. 



Figure 19. — Cephalon oi JUwnus ^ '^ 



Figure 20. — Cephalon of Proelus V Proetid.-E. 



Figure 21. — Cephalon of Sronieu.s |-Bronteidai. 



Figure 22. — Cephalon of iicAas j-Lichadidse. 



Figure 23. — Cephalon of Acidaspis J- Acidaspidfe. 



Proparia (Pages 152-157) 



Figure 24. — Cephalon of Placnpnria > Encrinuridre. 



Figure 25. — Cephalon of E)JC)-mt«nK ) 



Figure 26. - Cephalon of Cab/mmene f y^] ^.^enida). 



Figure 27. — Cephalon of Dipleura ^ ■' 



Figure 28. —Cephalon of Cheirurus (EccoptocheUe) j-Cheiruridse. 



Figure 29. — Cephalon of Dalmaniles ' 



Figure 30. — Cephalon of Dalmaniuv 



Figure 31. —Cephalon of Clmxmops \ Phacopidse. 



Figure 32. — Cephalon of Acasle 



Figure 33. — Cephalon of Phacops 



