24 



crown, of a subqnadrafe oi obtusely conical shape, convex externally. The canine or canine- 

 shaped premolar (r) is more than twice as long and broad as the incisor, with a sub- 

 compressed, sharp-pointed conical crown, a little inclined backward; it appears to have 

 been inserted by a divided root, like the similarly shaped and proportioned first premolar 

 in the Mole. The two succeeding teeth (l and 2) are one third smaller than the canine, 

 with subcomprcssed, conical crowns, at the fore and back part of which the base is slightly 

 produced ; each is implanted by two distinct fangs. The third and fourth teeth have a 

 similar form and complex implantation, but arc somewhat larger, and the basal cusps are 

 more developed ; in the fourth tooth this development gives a distinctly tricuspid charac- 

 ter to the crown, the middle cusp, representing the crown of the preceding teeth, being 

 the largest and highest. The six following teeth (5 to 10) repeat the same unequal tri- 

 cuspid form, with increased but varying size, the middle teeth (6,7,8) being the largest, 

 and the last tooth (10) diminishing in size in a greater ratio than the penultimate one (9). 

 These six last molar teeth are seen to be close together when the base with the ridge or 

 ' cingulum' is exposed. The lateral cusps incline inward, and project from a plane more 

 internal than the longer middle cusp. The inner side of the crown presents a wide lon- 

 gitudinal groove at the base of the middle cusp, between the inwardly inflected lateral 

 cusps ; the base of the crown presents externally a well-defined narrow cingulum, beneath 

 which the two fangs, or the two external fangs, descend into the substance of the 

 jaw. The last four teeth (7 — 10) show an inferiority of size, as compared with those of 

 fig. 32 a, which may be sexual. 



In the state in which this instructive portion of the Spalacothcre reached me, the 

 matrix concealed all save the large middle cusp of the molar teeth, which teeth seemed to 

 be wider apart, and presented a more lacertine aspect. By the careful application of a fine 

 needle and graving tool I succeeded in displaying the lateral cusps and grinding surface 

 of the crown, and the other teeth, as shown in the enlarged view given in fig. 33 a. Fig. 33 b 

 gives a magnified view of the antepenultimate molar (8), viewed obliquely from behind > 

 and fig. 33 c is an outline of the crown viewed vertically. We have here a right mandi- 

 bular ramus, with the outer side exposed. 



So much of the jaw-bone as is preserved in this specimen (fig. 33) nearly corresponds 

 in size and shape with the portion and impression of the opposite (left) ramus (fig. 32), and 

 shows the vertical contraction or decrease of that diameter behind the molar series, prior 

 to the expansion of the jaw into the ascending ramus. The horizontal ramus has suffered 

 an oblique fracture since its fossilization across the alveolar series, with a very slight 

 depression of the fore part containing the four anterior teeth ; a second fracture crosses the 

 contracted part of the jaw behind the last molar in place. There is not any clear evidence 

 of a smaller molar tooth behind the last in place, marked 10. Between the large laniari- 

 form tooth (c) and the fore end of the ramus of the jaw there is a space for three incisors 

 like the portion of the small one preserved (i), and also for a small canine-shaped tooth, 

 which is demonstrated in one of the specimens next to be noticed. 



