214 DE. C. J. FORSYTH MAJOR ON MIOCENE SQTTIREELS. [Feb. 28, 



(4) From the polybunous molar, as characterized before, have 

 been derived the other types of Placental molars, by a gradual 

 transformation of the longitudinal arrangement of cusps into a 

 transverse one {Chiastota.vis), and by a prevailing development of 

 a few cusps — a sort of Oligarchy — as well as by the fusion and 

 suppression of others, se^■eral of which are, hov\ever, maintained 

 with great persistency in a secondary condition. 



(5) In the upper molars two outer cusps and one or two inner 

 cusps are usually the most developed. 



(G) The truly tritubercular molar is Imt a vei'y specialized stage, 

 which is often preceded, not fuUowed, by Riitimeyer's trigonodont 

 type. 



(7) The supposition that the so-called heel or talon of inferior 

 molars is a later development, is an arbitrary one, disproved by 

 facts, 



(8) Which of all the cusps of the primitive polybunous molar 

 or its derivatives may be " homologous M'ith the reptilian cone,'' 

 I do not know. 



VI. EXPLANATION OF THE PLATES. 



Plate VII L 

 Right superior molars, much magnified, of: — 



Fig. L Sciuriis (Eosciiirits) indicus, Erxl. m,. (B.M. 1203a.) 



2. Sc.prevosfi,'Desm. m^. (B.M. 583(i.) 



3. Sc. lokroides, Hodgs. m,. (B.M. 18(i8/4 . 4.3.) 



4. Sc. everetti, Thos. ra^. (B.M. 1892/t) . fi.8.) 



5. Xerus (Eoxerus) kosci, Thos. pj. (B.M. 1892/7 . 19.2.) 



6. Xerus (F.oxerus) insigniSj'Pr. C\xy. m,. (B.M. 68 c.) 



7. Xerus {Prof oxcrus) sf a ngei-i,Wa.\.eYh. m,. (B.M. aloC.) 



8. A'eri/s (Protoxents) auhiiinii, Gr. m^ (B.M. 1875/4 . 30.4.) 



9. Xerns (Aikmtoxerus) qetulus, Gesn. m.^. 



10. Xerus crythupus, Geoff, m^. (B.M. 1888/11 .4.4.) 



11. Xerus {Eoxerus) latkaudatus, Gt. m^. (B.M. 1885/8 . 1.272.) 



12. „ ,, p,. 



13. Anomahirus fraseri,'V^B.i&Y\i. P|. (B.M. 555 c.) 



14. Anomahmis'beecrofti, Eras. m,. (B.M. 10G66. 188B/1 . 5.1.) 

 \b. Xerus {Paraxerus) pyrroj)US,'pT. Cu\. m,. (B.M. 897a.) 



16. Xerus {Eoxerus) berdmorei, Bly. (jnv.) m^. (B.M. 1878/6 . 17.51.) 



17. „ „ (middle age), m,. (B.M. 1878/6.17.33.) 



18. „ „ (old), m,. (B.M. 1861/4.12.13.) 



19. Pteromys leumgenys, Temm. m^. (B.M. 556 b.) 



20. Sciuroptcrus pearsoni, Gr. m^. (B.M. 1883 a.) 



21. Sciuropferushorsfeldi,Wnterh., type. m,. (B.M. 18,55/12 . 24.102.) 



22. A'eriis {Paraxerus) cepapi. Smith, m^. (B.M. 1885/12 . 8.2.) 



23. Xertis {Paraxerus) 2^!J'>'ropus anerythrus, Thos. mj. (B.M. 1890/6 



8.22.) 

 2i. Xerus {Paraxerus) isabella, Gr. m^. (B.M. 1862/5 .9.3.) Camerouns. 



Plate IX. 

 Right inferior molars, much magnified, of: — 



Fig. 1. Sciurus {Eoscijirits) iitdwus, Er.\l. m^. 



2. Bhithrosciuvus macrptis, Gr. mi. (B.M. 1888/8 . 13.7.) 



3. Sciurus lokroides, Hodgs, nij. 



4. Sciurus everetti, Thoa. m.,. 



