442 DR. C. I. POESYTH MAJOR ON 



cusps (8 & 9). Proceeding outward, we meet with two enamel folds starting from the 

 anterior side of the tooth. The one placed more internally (b) is hy far the larger of the 

 two ; it opens freely on the anterior side, and thence proceeds first internally, and then, 

 gradually attenuating, postero-externally, thus assuming approximately the form of 

 a crescent, whose anterior horn is much shorter than the posterior. Both horns are 

 delimited externally hy a cusp (6), having its long axis almost parallel to the long axis of 

 the skull, and protruding Avith its internal convex horder into the enamel fold just described, 

 while its shorter and almost longitudinal external border forms the inner margin of the 

 much smaller second enamel fold (c). On the outer side of the tooth we meet with a large 

 bulging enamel tubercle (5), worn by attrition on its inner side only, and showing thus that 

 the outer side in this otherwise much-worn tooth is only partially affected by trituration. 



The second tooth, p. 1, presents the general contour of the crown of lagomorphous 

 Rodents, the transverse diameter largely predominating over the longitudinal : the 

 anterior border is slightly more convex than the posterior. The minute pattern of the 

 triturating surface, however, is very different from that which we are accustomed to 

 consider characteristic of upper leporine molars. The main difference from p. 2 consists 

 in the two enamel folds being .shut out from the anterior border by a transverse anterior 

 lobe, Avhich in p. 2 is apparent only in a much reduced condition, its outer portion being 

 entirely wanting. In p. 1 the anterior lobe or " wall " delimits the anterior horn of 

 the enamel fold (b) on its front side, so that in this tooth the anterior horn is much more 

 lengtheued transversely than the posterior. As compared with p. 2, p. 1 has undergone, 

 as it were, a lateral pressure, by which the various parts of the surface have been forced 

 into a more transverse direction. This is apparent, especially in the strong cusp (6) 

 separating enamel folds Ij and c, which is no more longitudinally directed as in p. 2 

 but has likewise assumed the form of a crescent with its convexity projecting 

 inward into enamel fold b, and forming externally the inner margin of enamel fold c. 

 The latter has in its turn assumed a more transverse direction, and is only incompletely 

 shut out from the outer border of the tooth by a blunt enamel tubercle (5), occupying 

 mainly the postero-external part of the tooth. The summit only of this tubercle is 

 slightly worn. 



The inner border of p. 1 is more distinctly divided than in p. 2 into two abraded 

 cusps l)y a vertical groove, manifesting itself on the triturating surface in the shape of 

 a short enamel fold, or notch (a). 



The levelling effect of trituration — favoured by the enamel folds in both teeth being 

 more or less completely filled with cement, — together with the more transverse direction 

 assumed by the folds and cusj)s of p. 1, tends to produce a lophodout character of its 

 triturating surface ; or rather, we haA'e a selenodont type leaning towards lophodonty. 



3. Titauomys visenoviensis, from the Allier (France). Br. Mus. 31094 (Bravard Col- 

 lection). — A detached tooth (PI. 36, tig. 12) is more Avorn still than that just described, 

 as revealed by its triturating surface being more flattened and the enamel folds more 

 narrowed. It can only be either p. 1 or m. 1. P. 3 is quite out of the question, as, to 

 judge from its alveolus, it was a very small tooth ; p. 2 is reduced in its antero-external, 



