137 



of teeth, and thus supplies what was less perfectly shown in the subject of Plate XVII. 

 I may add that photographs, and specimens of this tooth (m 1) from the breccia-cave, 

 illustrate the constancy of character in the solitary spelaean example of the true or tuber- 

 cular molar series from the upper jaw of Thylacoleo. 



Of the first incisor (i 1), nearly one inch projects from the outer wall of the socket in 

 the subject of fig. 1, Plate VII. ; the inner wall (fig. 2, ib.) extends two lines lower down 

 the tooth. The dimensions of the outlet of the socket give those of the corresponding 

 part of the tooth, which very closely fits and adheres to the socket. The anterior 

 border of the exposed part of the incisor shows a moderate curve convex forward ; the 

 posterior border, three lines below the socket, shows, after a slight basal convexity, the 

 beginning of a curve concave backward. The exposed base of the tooth retains for four 

 or five lines below the socket a coating of cement beneath which the enamel emerges. 

 This is thicker toward the back than at the fore part of the crown, but nowhere exceeds 

 half a line. Much of it is broken away from the base of the crown here preserved ; and 

 at the outer and back part of the base of the crown the enamel presents a free rounded 

 edge, for two lines vertically, as if it were there interrupted. The dentine is extremely 

 dense ; the diameters of the broken part of the crown, which I take to be about halfway 

 from the pointed end of the crown, are 7 lines by 5-| lines ; the dentine here presents, 

 in transverse section, a narrow oval form, broader before than behind, and more convex 

 outwardly than on the inner side. 



Of the second incisor (i 2) one can infer from its socket that it had a root about 5 lines 

 in length, tapering to an obtuse point, and a crown measuring 4 lines in diameter at its 

 base. 



The third tooth which has been displaced from the somewhat larger socket opening 

 upon the premaxillo-maxillary suture, and which makes a slight prominence on the out- 

 side of the alveolar tract, at a short distance from the second, I conclude to have been a 

 canine (c) ; the fang, or implanted part, has been 9 lines in length, slightly curved, taper- 

 ing to the end. 



The tooth remaining in the socket (Plate VII. figs. 2 & 3, p 1) on the inner side of the 

 hind part of the canine (c) has the summit of the enamelled crown broken away ; the 

 diameters of the base of the crown are 4 lines and 3 lines. The root is firmly fixed in 

 the socket : I regard this as the first premolar (p 1). Its internal position, its implanta- 

 tion in the maxillary at^ some distance from the suture with the premaxillary, and its 

 continuation of the oblique line of the succeeding premolars, weigh with me against re- 

 garding it as a canine, according tothe hy pothesis of the tooth (c, Plate VII. figs. 1-3) 

 being a third incisor, as in some hypothetical restorations referred to in the sequel. 



Thesecond premolar (p 2) in situ in the specimen (Plate VII. figs. 1, 2, 3) is somewhat 

 smaller than p 1, with a very short enamelled crown, forming a low ridge extending 

 from the outer side to nearly the inner side, and there meeting and blending with a 

 second low ridge at right angles, close to the inner border of the crown. The enamel is 

 limited to forming the low-ridged cap or summit of the tooth ; the rest of the tooth 



