1873.] F. Stoliczka — Land-shells of Penang Island. 37 



groups. They will shew that certain characters remain constant under 

 different physical conditions, while others change, and that the change takes 

 place according to certain principles, affecting similar or the same organs. 

 Extended observations of this kind must give us the key to a correct sys- 

 tematic arrangement. 



Our special question cannot be solved, unless Blainville's and Ferussac's 

 somewhat contradictory accounts of the structure and anatomy of Vaginulus 

 Taunaysii had been satisfactorily settled. I hope to have myself an early 

 opportunity of examining one of these animals, and until such a time I will 

 postpone the detailed description of the Penang species, (and of another new 

 one from Sikkim), together with their anatomy, which requires a careful 

 comparison with that of Vaginulus and OncMdium^ of each of which I will 

 have to describe several interesting new forms. 



Ilxj^lanation of 'plates. 



Plate I. 



Figs. 1 — 3. Rhysota Cymatium, (Benson), p. 11 j a young-, an adolescent and an 



adult shell. 

 „ 4 — 7. Botula hijuga, n. sp., p. 14 ; four full grown specimens, variable in the 



height of the spire. 

 „ 8. Sitala carinifera, n, sp., p. 16 j 8, natural size j 8a, 86, 8c, enlarged 



views. 

 „ 9. MacTochlamys stephoides, n. sp., p, 17; three views in natural size. 



„ 10. Microcystis palmicola, n. sp., p. 18j 10, natural size j 10a, 10b, 10c, 



three views enlarged. 

 „ 11. Helicarion permolle, n. sp., p. 18 ; 11, twice the natural size j 11a, 11&, 



lie, lid, views in natural size. 

 }} 12. Vitrina nucleata, n. sp., p. 23 ; 12, front view in twice the natural size j 



12a, 12&, 12c, three views in natural size. 

 „ 13. Trocliomorpha Gantoriana, (Benson), p. 22 ; three views in natural size. 



„ 14 — 16. „ castra, (Benson), p. 21 ; 14, 14a, 14b, three views in na- 



tural size ; 15, side view of a specimen from Calcutta ; 16 and 16a, 



top and lower views of a Darjiling specimen. 

 „ 17. Timorensis, Mart., p. 22 ; four views in natural size. 



Plate II. 

 Fruticicola similaris, Fer., p. 26. 



Vitrina nucleata, Stol., p. 23 ; 4a, represents the side view of the proble- 

 matic amatorial organ enclosed in the bursa seminalis. 

 Trochomorpha castra, (Benson), p. 21. 



„ Timorensis, Mart. ; p. 22. 



Rhysota cymatium, (Bens.) ; p. 11. 

 Rotula hijuga, n. sp., p. 14. 

 Macrochlmnys steplioides, n. sp., p. 17. 

 Helicarion permolle, n. sp., p. 18. 

 All the figures are enlarged j the measurements in natural size are given in the 

 text referred to. 



igs, 



1—3. 



}} 



4—6. 



if 



7—9. 



ft 



10—12. 



It 



13—15. 



V 



16—18. 



9> 



19—20. 



a 



21—30. 



