Fig. 1. _a._ Skull of _Abrocoma Cuvieri_—natural size.
— 1. _b._ Side view of ditto.
— 1. _c._ _Ramus_ of lower jaw—outer side.
— 1. _d._ Lower jaw seen from above.
— 1. _e._ Molar teeth of the upper jaw magnified.
— 1. _f._ ditto of lower jaw.
— 2. _a._ Skull of _Reithrodon cuniculoïdes_.
— 2. _b._ Incisors of the upper jaw magnified.
— 2. _c._ Molar teeth of the upper jaw magnified.
— 2. _d._ ditto of the lower jaw.
— 2. _e._ ditto of upper jaw of a younger specimen.
— 3. _a._ Portion of a skull of _Mus Braziliensis_.
— 3. _b._ ditto, view of palate.
— 3. _c._ Molar teeth of the upper jaw magnified.
— 3. _d._ ditto of lower jaw.
— 4. _a._ Molar teeth of lower jaw of _Reithrodon typicus_
magnified.
— 5. _a._ Molar teeth of the upper jaw of _Mus canescens_.
— 5. _b._ ditto of under jaw.
— 5. _c._ Skull of ditto.
— 5. _d._ Posterior molar of the lower jaw more worn than in 5.
_b._
— 6. _a._ Molar teeth of the lower jaw of _Mus longipilis_.
— 6. _b._ Molar teeth of the upper jaw.
— 7. _a._ Skull of _Mus nasutus_.
— 7. _b._ Molar teeth of upper jaw.
— 7. _c._ ditto of lower jaw.
— 8. _a._ Skull of _Mus Galapagoensis_.
— 8. _b._ Molar teeth of upper jaw.
— 8. _c._ ditto of lower jaw.