560 Synopsis of the Trilohites of JVorth America. 



Genus Trimerus — Green. 

 T. Delphinocephalus — Green. Fig. 1. 



Clypeo semilunari, antice compresso ; oculis minimis, emineii 

 tissimis ; articulis duplicibus vix lobatis ; canda attenuata ; cor- 

 pora tuberculato. 



Genus Cryptolithus — Green. 



C. Tessellatus — Green. Fig. 4. 



Clypeo rotundato, fronte valde convexo, capita antice semi- 

 circulari, margine tessellato, ornato. 



Genus Dipleura — Green. 



D. Dekayi — Greeji. Fig. 9. fig. 8. caput. 



Clypeo lunato punctato; abdomine quatuordecim articulis 

 duplicibus vix lobatis ; cauda suborbiculari, limbo lato convexo 

 integerimo ; oculis oblique deflexis. 



Genus Isotelus — Dekay. 

 I. Gigas — Dekay. 



Clypeo antice ova to, acuminato, punctato ; cauda orbiculari ; 

 limbo lato ; articulis abdominis octo. 

 I. Planus — Dekay. 



Clypeo antice caudaque postice rotundatis ; articulis octo ; 

 corpore depresso. 

 I. Cyclops — Green. Fig. 7. 



Clypeo antice attenuato, piano ; oculis rotundis, proximis ; 

 cauda ovita, acuminata. 



Genus Triarthrus — Green. 

 T. Beckii — Green. Fig. 6. 



Cauda subrotunda, bipunctata ; articulis abdominis tribus, 

 absque lobis lateralibus consuetis, sed lobo arcuato utrinque 

 apposito. 



Genus Paradoxus — Brongniart. 

 P. Boltini — Bigsby. Fig. 5. 



For a description of this species see the fourth volume of the 

 Journal of the Academy of Natural Sciences. 

 Genus Ceraurus — Green. 

 C. Pleurexanthemas — Green. Fig. 10. 



Clypeo postice arcuato, angulo externo in mucronem valde 

 producto ; oculis minimis remotis ; postabdomine in spinam ar- 

 cuatam acutam utrinque extenso. 



