82 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 83 



The minimum thickness of the body (at first molar) of the Piltdown jaw is 

 1.45 cm. This is above the average of both human and chimpanzee jaws, but is 

 occasionally equalled and even exceeded in both. There is therefore nothing 

 distinctive in this respect. 



The e.xternal surface of the body shows the usual somewhat indistinct oblique 

 line. There is nothing characteristic in it for either man or chimpanzee. This 

 external surface shows also, however, an important feature that has so far 

 failed to receive due attention. This is a basal ridge forming a boundary between 

 the external surface proper of the bone, and the inferior flattening that gradually 

 enlarging proceeds under the fore part of the jaw where it forms a shelf such 

 as exists more or less in ape and other jaws that have a negative chin. The 

 ridge above this shelf is not found in modern man except rudimentarily. It is 

 already rather rudimentary in the Mauer jaw. It is well marked in the Pilt- 

 down jaw, and it is occasionally fairly well marked in an adult chimpanzee. 

 It is caused by the shelf but even more so by the large and long canine eminence 

 due to a large canine. It does not exist, or exists only in traces wherever the 

 canine tooth is small as in the chimpanzee females and the young, or in modern 

 man. Its presence in the Piltdown jaw seems a very strong indication that the 

 jaw possessed a relatively large canine tooth ; and this, with other considera- 

 tions, increases the probability that the Piltdown canine belonged to the jaw, 

 or at least to the same or a like skeleton. 



The development of the sub-mentoneal shelf in the Piltdown jaw equals that 

 of most chimpanzees — except, as already mentioned, in the solidity of the struc- 

 ture which in this case was plainly less than in any of the apes. A shelf of this 

 nature is found in none of the ancient human jaws, though they all show traces 

 of it. Traces of it may in fact be detected even in some modern jaws of man. 

 In this feature, and in the indicated presence of a relatively larger than human 

 canine, the jaw stands apart from all those of early man that have so far been 

 discovered, and is correspondingly nearer to the chimpanzee or some related 

 ancient anthropoid form. But neither of these features can be taken as con- 

 clusively diagnostic of a chimpanzee nature of the jaw. All that we would 

 seem to be justified in saying is that in these respects, as well as in one or two 

 others, the bone resembles more that of an ape than man. But as we cannot but 

 believe that the human lower jaw in its evolution must have passed through 

 such stages, these features do not legitimately hinder us, if other characteristics 

 so urge, from placing the jaw in the line of early man or his precursors. 



The lingual surface of the body of the jaw is quite smooth and presents noth- 

 ing distinctive for either man or ape except the height of the body which on the 

 inside even more than on the outside approaches the human type. The height of 

 the body from the middle of the lingual border of the 3M alveolus is 3.0 cm. ; 

 in the adult chimpanzees of the U. S. National Museum it was found to be 

 respectively 2.8, 2.7, 2.8, 2.5, 2.75, 2.4, 2.6, 2.85, 3.0, 2.7, 2.6, 2.9, and 2.6 cm. 

 In the Mauer jaw this height was 3.3 cm. ; while in modern human jaws a height 

 of 3 cm. or even slightly over is quite common in males ; in females it is lower. 

 If the Piltdown jaw represents a female, as seems most likely, the male jaw 

 of the same species would have been even higher and well beyond the range of 

 variation of the chimpanzee. 



The teeth. — The alveoli and interalveolar septa in the Piltdown jaw show 

 little that could be regarded as distinctive in form ; but they are larger antero- 

 posteriorly, particularly in the case of the 3M, than in any chimpanzee available 



