132 REFERENCES TO THE PLATES. 
Figs. 3, 4. Lateral views. a, Crown, on the inner surface invested with enamel; 6, fang, grooved 
on the inner part for adaptation to the outer border of a successional tooth; c¢, surface, impressed 
apparently by contact with the side of the apical half of the crown of an infero-lateral successional 
tooth; d, portion of the denticulated enamel border of the crown magnified about six diameters. 
Figs. 5-7. An inferior tooth with the apical half of the crown worn off. 
Fig. 5. Outer view. 
Fig. 6. Inner view. 
Fig. 7. Lateral view. a, Triturating surface of the crown; 3, cutting edge of the triturating 
surface. 
Figs. 8, 9. An inferior tooth with the summit of the crown worn off. 
Fig. 8. Outer view. 
Fig. 9. Lateral view. 
Figs. 10-13. A superior unworn tooth, with the greater portion of the fang lest. 
Fig. 10. Outer view of the crown invested with enamel. 
Fig. 11. Inner view. 
Figs. 12, 13. Lateral views. a, Surface impressed by the apical half of the lateral successional 
teeth ; 6, surface impressed by the outside of the apex of the successional tooth above or in the same 
line; c, strong carina of the external enamelled surface of the crown. 
Figs. 14-17. A superior tooth with the summit of the crown worn off. References as in the pre- 
ceding tooth. 
Figs. 18, 19. Ideal representation of the supposed arrangement of the teeth of Hadrosaurus in 
the relationship of the functional and successional teeth. 
Fig. 18. External view of the relationship of the inferior teeth. a, Triturating surfaces of the 
teeth; b, teeth with the apical half of the crown worn away; c, tooth with its apex d, worn off; 
e, tooth worn away to the fang. 
Fig. 19. Internal view of the relationship of the inferior teeth. a, Inner cutting edge of the 
triturating surfaces; 6, teeth with the apical half of the crown worn away; ¢, an unworn tooth; 
d, tooth with the crown little more than half developed. : 
Figs. 20-23. Mutilated tooth of Astrodon Johnstoni, natural size, from Bladensburg, Md., belong- 
ing to Dr. C. Johnston. : 
Fig. 20. Outer view. 
Fig. 21. Inner view. 
Figs. 22, 23. Lateral views. 
Figs. 24-26. Fragments of the jaws of Hadrosaurus, one-half the diameter of the originals. 
Fig. 24. Inner view of a fragment of the lower jaw, exhibiting the alveolar grooves. 
Fig. 25. Outer view of the same specimen, much mutilated. 
Fig. 26. Inner view of a fragment supposed to belong to the upper jaw. 
Figs. 27, 28. Supposed sacro-vertebral body of a young Hadrosaurus, from Monmouth Co., New 
Jersey, one-half the diameter of the original. 
Fig. 27. Side view. 
Fig. 28. Inferior view. 
Polat Heo Ve 
Hadrosaurus Foulkii. Bones of the limbs, one-fourth the diameter of the originals. 
Figs. 1-4. The left humerus. 
Fig. 1. Posterior view. 
Fig. 2. Anterior view. 
Fig. 3. External view. 
Fig. 4. Upper extremity. a, Head; b, internal tuberosity; c, external tuberosity; d, deltoid 
attachment. 
Fig. 5. Anterior view of the left ulna. 
Fig. 6. Anterior view of the left radius. 
