Part 5

— 6. b. ditto of lower jaw.

— 7. a. Skull of Mus arenicola.

— 7. b. Molar teeth of upper jaw.

— 7. c. ditto of lower jaw.

— 7. d. Ramus of lower jaw.

— 8. a. Molar teeth of upper jaw of Mus brachiotis.

— 8. b. Two posterior molars of lower jaw.

— 9. a. Molar teeth of upper jaw of Mus obscurus.

— 9. b. ditto of lower jaw.

— 10. a. Ramus of lower jaw of Mus nasutus.

— 11. a. Molar teeth of lower jaw of Mus tumidus.

— 12. a. Ramus of lower jaw of Mus Braziliensis.

— 13. a. Molar teeth of upper jaw of Mus micropus.

— 13. b. ditto of lower jaw.

— 14. a. Ramus of lower jaw of Mus Galapagoensis.

— 15. a. Molar teeth of upper jaw of Mus griseo-flavus.

— 15. b. ditto of lower.

— 16. a. Molar teeth of upper jaw of Mus xanthopygus.

— 16. b. ditto of lower jaw.

— 17. a. Molar teeth of upper jaw of Mus Darwinii.

— 17. b. ditto of lower.

— 18. a. Molar teeth of upper jaw of Mus Gouldii.

— 18. b. ditto of lower.

— 19. a. Molar teeth of upper jaw of Mus insularis.

— 19. b. ditto of lower jaw.

— 19. c. Portion of ramus of lower jaw.

— 20. a. Skull of Reithrodon chinchilloïdes—natural size.

— 20. b. ditto, viewed from beneath.