478 DE. C. I. rOESTTH MAJOR ON 



supplements this description by the following information based upon a great number of 

 remains : — " 1 am able to show that it is only in the immature state of the first molar 

 that it exhibits a double column, and that in the fully adult animal it consists of a 

 single column with a groove on its external face " *. A more complete description is 

 given on p. 878 : — " There is the merest trace of a posterior lobe " — corresponding to the 

 termiual lobe (/) of Tltanomys — "at tliis time, and that speedily disappears. The 

 anterior lobe is subconical, and is entirely surrounded with enamel. By attrition, the 

 two lobes are speedily joined by an isthmus, and for a time the tooth presents an 

 8-shaped section, which was supposed to be characteristic of the genus. Further 

 protrusion brings to the surface the bottom of the groove of the inner side of the shaft, 

 so that its section remains in adult age something like a B." From this description it 

 appears that p. 2 of Falceolagus Maydeni is almost exactly like the same tooth in 

 Titanoniys Fontannesi. 



The difference between the p. 2 of Talffolagus and Lepus is stated by Cope to be as 

 follows : — In the extinct genus the first tooth " consists of one column more or less 

 divided. In Lopus this tooth consists of two columns, the anterior of which is grooved 

 again on the external side in the known species." Leidy's description of the Leporine 

 p. 2, as being composed of three lobes or columns, is more accurate. It is quite true 

 that in the adult p72 of many Leporidaj appears to be composed of two columns, witli 

 an additional antero-external enamel-inflection (see Pi. 37. figs. 13 & 19) ; but by no 

 means universally so, and, so far as my experience goes, it is neA'er so in the young 

 (PI. 37. figs. 8, 18, 22, 23). 



In the immature p7^ of Lcinis s. 1. (PI. 37- figs. 8, 22), as well as in the immature stage 

 of all the other inferior molars of the same, the posterior and the middle-lobe column are 

 completely divided ; only in later stages a very ]iarrow isthmus of dentine connects them 

 on the inner side (PL 37- figs. 33, 20, 23). The fact of a primary separation into two 

 lobes of the inferior molars of Lepxis was first announced by Hilgendorf +. 



The unworn lower p. 2 of the "Wild Piablnt (PI. 37- fig- 8) displays anteriorly the 

 anterior of the three columns completely divided into a smaller outer and a larger inner 

 subconical cusp ; this division is brought about by a longitudinal enamel-inflection, 

 which invades part of the middle lobe as well, so that the latter is also divided, though 

 incompletely, into an outer and an inner cusp. (Compare the homologous enamel- 

 inflection of Prolacpis, fig. 9.) 



Passing on to the lower cheek-teeth backAvard from p. 2, the various stages which I 

 have represented in PI. 37 show in the lower molars the simple transverse pattern of the 

 two lobes of p. 1 ; m. 2 is a secondary one, as in Ihe ujiper teeth, though in the inferior 

 molars the original pattern is much more ephemeral, least so in p. 1, which forms a 

 transition between p. 2 and the true molars. 



* ' The Yertebrata of the Tertiary Formations of the West,' p. 874, pis. ')(! & 57 (1883). t Op. cit. p. 870. 



X " Bcstebeu die unteren Backziihiie anfaiigs aus z-nei getrennteii Schmclzlamellcii, 'welche erst spiiter mit 

 ciuaiicler verwachsen, so class cin wcsciitlicher TTiitcrschicd z-\vischen zusammengesctzten mid schmclzfaltip;eii Zahnen 

 dcr hasenartigcn Thiere nicbt zu machen ist ."' Monatsher. d. K. preiiss. Akad. d. Wiss. zu Berlin. Sitzg. v. 14. 

 Dee. 1SG5, p. G73 (1800). 



