PROTREMATA (PAGE 245) 



FIGURE 13. Dorsal protegulum and early nepionic growth-lines 

 of Plectambonites segmentina Angelin. X 80. Upper Silurian, Gotland, 

 Sweden. 



FIGURE 14. Dorsal protegulum of Chonetes scitulus Hall. X 80. 

 Hamilton Group, Thedford, Ontario. 



FIGURE 15. Ventral protegulum of Chonetes granuliferus Owen ; 

 showing pedicle-notch. X 80. Coal Measures, Manhattan, Kansas. 



FIGURE 16. Nepionic stages of ventral valve of Orthoihetes elegans 

 Bouchard. X 25. (Compare with figure 12 of Acrothele.) Devonian, 

 Ferques, France. 



FIGURE 17. Nepionic stages of Stropheodonta perplana Conrad ; 

 showing pedicle perforation, deltidium, and hinge-area. X 25. Hamil- 

 ton Group, Falls of the Ohio. 



FIGURE 18. Ventral nepionic stage oiLeptcena rhomboidalis Wilckens. 

 X25. 



FIGURE 19. Profile of the same. X 25. 



Lower Helderberg Group, Albany county, New York. 



FIGURE 20. Hinge of a specimen 2 mm. in length ; showing deltid- 

 ium and hinge-area. 



FIGURE 21. Ventral view of specimen having same dimensions ; 

 showing nepionic and neanic stages, and relative proportions of pedicle- 

 opening and shell at this stage. Niagara Group, Waldron, Indiana. 



Figures 20 and 21 are taken from "Development of Some Silurian 

 Brachiopoda," Mem. N. Y. State Museum, vol. i, no. 1, pi. ii, figures 2, 12, 

 1889. 



TELOTREMATA (PAGES 245, 246) 



FIGURE 22. Ventral view of young Kraussina (Megerlina) Lamarcki- 

 ana Davidson ; showing protegulum and early nepionic stages. X 80. 



FIGURE 23. Dorsal view of same; showing dorsal protegulum and 

 pedicle-opening in ventral valve. X 80. 



Recent, Port Jackson, Australia. 



FIGURE 24. Dorsal view of beaks of young Terebratulina septen- 

 trionalis Couthouy; showing dorsal protegulum and pedicle-opening in 

 ventral valve. X 80. Recent, Eastport, Maine. 



FIGURES 25-28. Diagrammatic representation of ventral areas ; 

 showing progressive development of deltidial plates. 



Figure 25 is without plates, as in ventral area of figure 23. Figure 26 

 shows two triangular plates, which unite by symphysis in figure 27, 

 making an elongate pedicle-opening. In figure 28 the pedicle perforation 

 is sub-circular and truncates ventral beak. This series corresponds 

 essentially with that shown in Rhynchotreta cuneata Dalman, in " Develop- 

 ment of Some Silurian Brachiopoda," loc. ciV., pi. iv, figures 16-22. 



