PROTREMATA (Page 245) 



Figure 13. — Dorsal protegulum and early nepionic growth-lines 

 ol' Pleclamboniles segmenlina 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 Orthothetes elegans 

 Bouchard. X 25. (Compare with figure 12 of Acrolhele.) 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 of Leptcena rhomboidalis AVilckens. 

 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 

 Braohiopoda," Mem. N. Y. Stale 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 TerehraluUna septen- 

 trioncdis 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 Rhyncholrela cuneala Dahnan, in " Develop- 

 ment of Some Silurian Brachiopoda," loc. cil., pi. iv, figures 10-22. 



