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



remainder of the ridges (nine) are contained in a space of 4'2 inches ; so that by making 

 the same allowance for the lost portion as in the cases of the Zebbug molar and 

 No. 28', there would have been fourteen ridges in about 5^ inches, i. e. supposing the 

 teeth to have been last true molars. At all events it is clear that their ridge-formulas 

 exceeded ten plates and two talons. This is further shown by the following, which re- 

 presents the palatal region containing a fragment of the left and almost the entire right 

 molar in situ. 



3. The specimen in the B. M. (No. 87) has been much injured, and the posterior talon 

 has been recently lost. The crown is not nearly so far advanced in wearas the last, the four 

 posterior ridges being intact. There is a small field of dentine in front, 0-3 inch, and 

 sufficient to have maintained an extra ridge. As the tooth stands, tliere are thirteen 

 ridges in 5-5 inches ; and from its state of wear it may be said to be entire, with the 

 exception of the loss of the last ridge. In crown-constituents it repeats precisely the 

 characters of the preceding, and from its long graduating crown indicates at all events 

 the usual contours of the penultimate and last upper true molars. The crown-pattern in 

 PI. IV. fig 1 and No. 87 are precisely alike, and also correspond with the two pre- 

 ceding. Now, in comparison with No. 28 and the Zebbug molar, it will be found that 

 the two just described contain an extra ridge in a given space ; thus the two former 

 hold seven ridges in the same space occupied by six ridges in the two latter. 



4. One of the most characteristic and instructive specimens in my collection is the 

 portion of a right lower ramus. No. 95 (PI. VI. fig. 1), containing an entke molar 

 (fig. 1«) which has been detached and is represented of the natural size in order to 

 show its outline. Here we have the character not rare in last true molars of recent and 

 fossil species when the posterior ridges become reclinate, so that the posterior talon c 

 (fig. I a) is nearly horizontal. The tooth in this instance fills the ramus, so that its base 

 posteriorly reaches to b (fig. 1), or in other words, within a short distance of the opening 

 of the dental foramen. There is an indication of the bony alveolar septum behind ; so 

 that, to all appearance, the only conclusion we can come to is that the molar is the 

 last of the dental series. It contains fourteen ridges in about G inches. Excepting 

 the ten disks in wear, the remainder of the coUines are more or less hidden by the 

 investing cement ; but their tips are determinable. 



It will be seen from fig. ] a that the ridges are crowded, and that the enamel is 

 decidedly thin as compared with the upper teeth ; there is faint crimping, however, with 

 central expansions and angulations on the well-worn disks. It may be here observed 

 that the surface in wear represents the entire attrition-plane, as no fragment of a pre- 

 ceding molar is noticeable. From this circumstance, therefore, and the space occupied 

 by the tooth, it seems to me to afi'ord conclusive proof of its being a last true molar of 

 a very small species of elephant. 



' I have invariably estimated the average width of the ridges by measurements taken at the base of the crown, 

 so as to overcome the errors likely to arise from measuring disks in various stages of wear. 



