PLATE VIII 

 TRIARTHRUS BECKI GREEN (PAGES 205-211) 



FIGURE 1. Diagrammatic restoration of second thoracic limb in 

 transverse section of trilobite; showing gnathobases extending under 

 the axis toward the median line, and the biramous limbs under the pleura 

 and beyond the carapace. 



FIGURE 2. Diagrammatic restoration of anterior pair of pygidial 

 limbs ; showing phyllopodiform structure. 



FIGURE 3. Diagrammatic restoration of posterior pair of pygidial 

 limbs ; showing more strongly the primitive phyllopodous structure. 



FIGURE 4. Dorsal view of second thoracic leg, with gnathobase. X 12. 



FIGURES 5, 6, 7. Dorsal views of three heads; showing antennules. 

 Their position in figure 7 is the most common. 



FIGURE 8. Portion of under side of head ; showing plate-like gnatho- 

 bases of cephalic limbs, posterior part of hypostoma, the metastoma, and 

 one endopodite on the right. X 4. 



FIGURE 9. Under side of head, with gnathobases and metastoma 

 better preserved. X 4. 



FIGURE 10. Under side of head ; showing antennules and their 

 points of attachment, the four pairs of gnathobases of the other cephalic 

 limbs, and the hypostoma and metastoma in the median line. X 4. 



FIGURE 11. Diagram; showing the cephalic appendages preserved 

 in figures 5, 6, 7, and figure 1, Plate VII. 1, shaft of antennule bearing 

 a single flagellum ; , coxopodite of first pair of biramous limbs, or pos- 

 terior antennae ; #, third pair of cephalic limbs, or mandibles ; 4, 5, 

 gnathobases of fourth and fifth pairs of cephalic limbs, or maxillaa ; %, 

 hypostoma; m, mouth; met, metastoma; s, setae. This figure is not in- 

 tended as a complete restoration of the cephalic appendages, but only as 

 a diagram for convenient reference, combining the characters preserved 

 in the specimens illustrated. 



FIGURE 12. Portion of the under side of the head and thorax of 

 Apus. hy, hypostoma; J?, antennule; #, posterior antenna ; 5, mandibles; 

 4, 5, maxillae ; 6, maxilliped ; 7, first thoracic leg ; 8, 9, basal endites of 

 phyllopodiform legs. X 3. 



