DETERMISATIOS OF A(;i: IS HATS. j.-,:5 



ilitierent aspect to the surface of the tooth. If cusp 5 lias very 

 uearly, but not quite, disappeared, the inner (median) maroin of 

 the conthieut worn surfaces of commissures 2-5 and o-o closely 

 approaches, but is not in contact w ith. the opposite margin of tlie 

 worn surface of cusp (lig. V aj. V'ig. V b represents an indi- 

 vidual in which the two margins actually touch each otliei'. Final- 

 iv. Fig. y c, an individual in which these margins have disappeared, 

 so that the worn surface of cusp G is coulluent not only in front 

 with commissures 1-4 and 2-4, but also posteriorly with commis- 

 sures 2-5 and 3-5, and the deep pit, which in the less worn tooth 

 separates cusp 4 from cusp 5, has been transformed into an island 

 pit in the centre of the tooth. I have alread}^ alluded to tlie fad 

 that these degrees of wear of cusp 5 are undoubtedly purely indi- 

 vidual ; the five October skulls representing this fifth stage of wear 

 show perfect intergradations in this respect. 



These are the stages of wear represented in a series of forty 

 skulls of Bldnoloplius r. roiAxi from October and November (Soutli 

 Mysore and South Mahratha Country). \"arious reasons have led 

 me to the conclusion that they are five consecutive stages, with one 

 year between : — 



First, the amount of wear leading from stage I. to II. is similar to 

 that leading from II. to III, or from III. to IV, or from IV. to V, 

 if we bear in mind the fact that the ratio of wear is gradually acce- 

 lerated in proportion as the enamel coat is more and more comple- 

 tely worn away from the surface of the tooth. With this necessarj- 

 Cjiialification the stages are evidently equidistant so far as the 

 amount of wear is concerned, and it appears reasonable to deduce 

 that they are equidistant in point of time as well. 



Second, I have submitted this conclusion to the test of all other 

 available skulls of Eh. r. roiixi in so far as these are exactly dated. 

 Apart from the forty October-November skulls, I have examined 

 sixty-four from the months of Januar}^, February, April, and May, 

 all from the same geographical district (N. Kanara, Savantwady, 

 Konkan). Every one of these sixty-four skulls is easily referable 

 to one or other of the five stages described above, allowing of course 

 for the slight additional wear due to the more advanced season ; the 

 main point is, that there is no trace of the existence of any other 

 " stage." Our series really seems to be complete, so far as it goes. 

 It may be necessary to add these words, " so far as it goes," for 

 it is just possible that a sixth stage occurs, one year beyond the 

 fifth. I should hesitate to consider it probable, seeing- that in the 

 fifth stage the molars are practically reduced to the very level of the 

 gums, but on the other hand it is not absolutely inconceivable that 

 a sixth stase exists, thouo;h it would no doubt be rare. 



Presuming, therefore, that our series is complete, we liavo of 



