Fig. 1. _a._ Skull of _Mus longicaudatus_—natural size.
— 1. _b._ Molar teeth of upper jaw of ditto.
— 1. _c._ ditto of lower jaw.
— 1. _d._ _Ramus_ of lower jaw—natural size.
— 2. _a._ Skull of _Mus elegans_—natural size.
— 2. _b._ Molar teeth of upper jaw.
— 2. _c._ ditto of lower jaw.
— 3. _a._ Skull of _Mus bimaculatus_—nat. size.
— 3. _b._ Molar teeth of upper jaw.
— 3. _c._ ditto of lower jaw.
— 3. _d._ _Ramus_ of lower jaw—natural size.
— 4. _a._ Skull of _Mus gracilipes_.
— 4. _b._ Molar teeth of upper jaw.
— 4. _c._ ditto of lower jaw.
— 4. _d._ View of the under side of the tarsus.
— 5. _a._ First and second molar teeth of upper jaw of _Mus
flavescens_.
— 5. _b._ Two posterior molar teeth of the lower jaw of ditto.
— 6. _a._ Molar teeth of the upper jaw of _Mus Magellanicus_.
— 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.
— 20. _c._ ditto, side view.
— 20. _d._ _Ramus_ of lower jaw—natural size.
— 20. _e._ Molar teeth of upper jaw.
— 20. _f._ ditto of lower.
— 21. _a._ Skull of _Reithrodon cuniculoïdes_, viewed from beneath.
— 21. _b._ ditto, side view of fore part.
— 21. _c._ _Ramus_ of lower pair.
— 22. _a._ Hinder part of ramus of lower jaw of _Abrocoma
Bennettii_.
— 23. _a._ Skull of _Abrocoma Cuvieri_, viewed from beneath.
— 23. _b._ Lower jaw of ditto, viewed from beneath.
— 23. _c._ _Ramus_ of lower jaw, inner side.
— 24. _a._ _Ramus_ of lower jaw of _Octodon Cumingii_, inner side.
— 25. _a._ Skull of _Didelphis crassicaudata_.
— 25. _b._ ditto, viewed from beneath.
— 25. _c._ Side view of fore part of skull.
— 25. _d._ _Ramus_ of lower jaw, outer side.