SPIRIFER RADIATUS SOWERBY (PAGES 382-386) 



FIGURE 9. A cardinal view ; showing a similar stage of develop- 

 ment of the deltidiuin ; from an individual which has not attained normal 

 full-growth. 



FIGURE 10. The youngest growth-stage observed. 



FIGURE 10a. Outline profile of the same. 



FIGURE 11. Dorsal view of a normal adult. 



FIGURE 11 a. Profile of the same. (28/7* Ann. Rept. N. Y. State 

 Mus. Nat. Hist., pi. 24, figs. 23, 25.) 



ATRYPA RETICULARIS LINN^US (PAGES 356-360) 



FIGURE 12. The incipient shell ; having a length of 2.25 mm. The 

 deltidial plates have already begun to form, and the shell has developed 

 two growth-lines. 



FIGURE 12. Outline profile of the same. 



FIGURE 13. Ventral view of a full-grown individual. 



FIGURE 13a. Profile of the same. (28^ Ann. Kept. N. Y. State 

 Mus. Nat. Hist., pi. 25, figs. 46, 47.) 



FIGURE 14. A series of outlines of the anterior margin of the valves; 

 showing the rapid increase in plications and the reversion from the em- 

 bryonic fold and sinus to the sinus and fold of maturity. 



FIGURE 15. The deltidial characters of the specimen represented in 

 figure 12. 



FIGURE 15a. Outline profile of the same. 



FIGURE 16. Similar view of a specimen measuring 3X3 mm. 



FIGURE 16a. Outline profile of the same. 



FIGURE 17. Similar view of a specimen measuring 3.5 X 4 mm. 



FIGURE 17a. Outline profile of the same. 



FIGURE 18. Similar view of a specimen measuring 8x7 mm. 



FIGURE \Sa. Outline profile of the same. 



FIGURE 19. Similar view of a specimen measuring 21 X 20 mm. 



FIGURE 19a. Outline profile of the same. 



FIGURE 20. Similar view of a full-grown specimen measuring 

 24 X 22 mm. 



FIGURE 20a. Outline profile of the same. 



