Ox THE STRUCTURE AND CLASSIFICATION OF THE TrEMATASPIDAE. 33 



Explanation of Plates. 



Plate I. 



Fig. 1. Enlarged view of the ventral margin of the dorsal shield, showing the rounded 

 prominence at a, the small processes b, and the larger serrations at g, h, i and j. 



Fig. 2. Enlarged view of the median dorsal openings, showing de bony framework on the 

 floor and sides of the orbits. 



Fig. 3, Section through de margin of the shield, showing the bony trabeculae uniting the 

 dorsal and ventral shields. 



Fig. 4. Section through the anterior median opening. 



Fig. 5. Sectiou through the orbits, showing bony trabeculae on the sides of the same. 



Fig. 6. Section through the posterior median portion of the dorsal shield, showing the pro- 

 jecting processes on its inner surface, for the the attachment of muscles. 



Fig. 7. Small plate of unknown origin and significance. 



Plate II. 



Fig. 8, 9 and 10. Three views of a wax model of Tremataspis Schmidti. In fig. 8, the oral 

 plates on the right, including the triangular median one, are reproductions of a cast 

 in the St. Petersburg Academy. The plates on the left, and the ventral margin of 

 the dorsal shield are partly restored. 



-f*K*^ 



PRESBIJTED 

 30 Alia 1907 



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