PLATE VI 

 TRIARTHRUS BECKI GREEN (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 antennae bent outward and backward. 



FIGURE 5. Cephalon with slightly diverging antennae 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 diameters. 



FIGURE 8. Appendages attached to right side of second and third 

 thoracic segments ; taken from another specimen. 



FIGURE 9. The same; with setae omitted from 77, to show details 

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

 on 777. X 12. 



Utica Slate, Ordovician, near Rome, New York. 



