THE MOLLUSCAN KADULA. 135 



10. LovEN.— ' Ofv. Ak. Foih.,' 1847. 



11. V .MiDDENDOKF.— 'Mem. Ac. St. Petersb.,' 1847. 



12. W. OsLER.— ' Phil. Traus.,' 1832, p. 97. 



13. Poll — ' Testacea utriusque Sicilise,' 1791. 



14. RiJCKEK.— 'Ber. Oberhess. Ges.,' 18S3. 



15. RossLEii. — ' Zeitsclir. wiss. Zool.,' xli, 1885, p. 417. 



16. RoTTMAXN.— Ibid., Ixx, 1901, p. 651. 



17. ScHNABEL. — Ibid., Ixxiv, 1903, p. G51. 



18. Sharp. — 'Inaug. Dissert. Wiirzbuig,' 1883. 



19. SoLLAS.— 'Proe. Dublin Soc.,' 1885, ii.s., vol. iv, p. 374. 



20. Sterki.— 'Proc. Amer. Piiil. Soc.,' 1893. 



21. SwAMMERDAM. — ' Biblia Naturae,' Leyden, 1737; 'Bibel der Katur 



Leipzig, 1753 ; ' Book of Nature,' 1757. 



22. TfiosCHEL.— ' Arcli. Naturg.,' i, 1836. 



23. Trosciiel. — ' Das Gebiss der Sclmecken,' 1856-1863. 



24. Van Beneden. — ' Auu. Sci. uat.,' 1835. 



EXPLANATION OF PLATE 9, 



Illustrating Miss Igerna B. J. Sollas' paper on "The Molluscan 

 Radula: its Chemical Composition, and Some Points in 

 its Development." 



Fig. 1. — Lateral teeth of Patella vulgata, isolated by nitric acid. 1, 

 Two inner laterals (with broken cusps), showing the overlap of the basal 

 pieces; 2, an outer lateral; 3, an inner lateral; 4 and 5, basal pieces from 

 which the cusps have become detached. 



Fig. 2. — Lateral teeth of Patella vulgata which have been subjected to 

 the action of nitro-hydrochloric acid in a sealed tube. 



Fig. 3. — A portion of the ash of an incinerated radula of Patella vul- 

 gata. 



Fig. 4. — a, A siliceous basal plate from the radula of Acmaea virginea 

 bearing three cusps, isolated by nitric acid, b, c, The same less magnified and 

 showing the three cusps separated from the basal piece, by further action of 

 nitric acid, and adhering together. 



Fig. 5. — A siliceous basal plate from the radula of Acmaea saccharina 

 bearing cusps. 



