24 ME. A. L. ADAMS ON THE OSTEOLOGY OF 



regard to the thin enamel and plates ; but the comparisons as regards length present 

 anomalies in the upper molar. Thus the difference in length between the members of 

 A Series and the Zebbug upper molar' is not by any means disproportionate ; but the 

 members of B Series are about the same length, although not nearly so broad, nor are 

 their crowns so high. Nevertheless, allowing for individual differences, it might be 

 concluded that this series represents the first true molar of the smallest form, which 

 ordinarily held eleven ridges, or nine plates and two talons. 



3. Reverting to the antepenultimate milk-molar (PI. I. fig. 3) it has been stated that 

 the jaw which contained it held also a germ penultimate milk-tooth of the dimensions 

 of the largest specimens (to wit, figs. 13 & 14), which differ from the smaller penulti- 

 mate milk-teeth (figs. 7 & 8) in size, ridge-formula, and development of the crown- 

 constituents. The former moreover display a highly rugous and digitated condition of the 

 collines, especially posteriorly, as seen in fig. 14. Now all these characters are repeated 

 in the members of D series, viz. the upper molar (PI. III. figs. 4, 4 a, & 46) and the 

 lower (figs. 5 & 5a), whilst the proportion in length between the two sets stand, as 

 regards upper teeth, as 2 to 3 '2 inches, and in lower as 2-4 to 3'4 inches. Indeed 

 these molars differ collectively so widely from their congeners in crown-pattern, plates, 

 and size, that I scarcely think there can be a doubt as to their independent characters. 

 The thickness of the plates and enamel as compared with other milk-molars, the less 

 rhomboidal-shaped disk, and the presence of pronounced crimping of the machserides 

 on newly invaded, and faint crimping on well-worn crowns, seem to me to distinguish 

 these much larger teeth from those of the smallest form. 



The ridge-formula, therefore, deducible from the above data would, as regards the 

 milk-series of the largest form, stand as 5:8:10-11, or, without the anterior and 

 posterior talon, 3:6: 8-9, being one ridge more in the penultimate milk-tooth than 

 obtains in the smallest form. 



4. If we admit the members of D series to represent the last milk-molar of the 

 largest form, there can be, I think, little doubt that E series wiU illustrate its succes- 

 sional first true molar. Irrespective of size, which entirely excludes the latter from all 

 the preceding, their relatively thicker plates and enamel claim for them the position 

 of true molars. As regards the thickness of plates and cement and discal pattern, how- 

 ever, they bear a close resemblance to the last milk-teeth just referred to, as may be 

 seen by comparing PI. VIII. fig. 5, and PI. III. figs. 3, 3«, and PI. IV. figs. 4 & 5, with 

 PI. III. figs. 4, 5, and the other well-worn crown of the latter (PI. IV. fig. 2 a). The 

 relative proportions between the last milk-teeth and members of E series are, as regards 

 upper molars as 3-2 to 4-3 inches, and lower as 3-4 to 5 inches. 



The ridge-formula, therefore, of the first true molar of the largest form of Elephant 

 would stand as in its last milk-tooth, viz. ten to eleven ridges, or eight to nine plates 

 and two talons. 



' Trans. Zool. Soo. vol. vi. pi. 53. figs. 9 & 9a. 



