PLATE VI 

 TRIARTIiRUS BECKI Gueen (Pages 199-202) 



Figure 1. — Dorsal view of larva. X 28. 



Figure 2. — Dorsal view of young individual, with one free thoracic 

 segment. (After Walcott.) 



Figure 3. — Cephalon with antennae nearly at right angles to axis. 

 The thorax and pygidium are omitted in figures 3-6. The figures are 

 enlarged 3-5 diameters. 



Figure 4. — Cephalon with antenna bent outward and backward. 



Figure 5. — Cephalon with slightly diverging antenute directed for- 

 ward, — the usual position in the majority of specimens. 



Figure 6. — Cephalon with antennae curving backward between the 

 eyes. 



Figure 7. — Dorsal view; showing antennae and crawling and swim- 

 ming legs. X 3. The legs on the left side are taken from a smaller speci- 

 men and are enlarged 6 diametei-s. 



Figure 8. — Appendages attached to right side of second and third 

 thoracic segments ; taken from another specimen. 



Figure 9. — The same ; with setfe omitted from //, to show details 

 of structure; ex, exopodite; en, endopodite. The setfe are represented 

 on ///. X 12. 



Utica Slate, Ordovioian, near Rome, New York. 



