600 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1914. 
, 
ler’s sea cow (Rhytina gigas), had “chins”’ also, but in a less marked 
form. As amatter of fact the downward prolongation of the mandible 
in these animals is not a chin comparable with our own at all, but 
is merely a kind of bony rostrum on which the dugong and its relations 
wear their horny false teeth. This structure, with its curious change 
of angle, is more comparable to the bony support of the flamingo’s bill 
than to ahuman chin. A very curious fact is that we appear to find 
the nearest resemblance in the whole animal world, whether ancient 
or modern, to our own mandible in a group of some of the earliest rep- 
tiles that have yet been discovered. In the figures 4 and 5 of those 
strange theromorphs, Pariasaurus and Inostransevia, unearthed by 
Prof. Amalitzky in the Permian strata on the shores of the northern 
Dwina, we see an extraordinary chin which resembles our own in 
several striking anatomical particulars. 
How such a resemblance comes to exist I do not even venture to 
guess; but most assuredly nature’s molding forces, which so shaped 
the mandibles of these ancient reptiles, were totally different from 
those cerebral activities largely responsible for the chin of civilized 
man. Wesay so more confidently because casts of their skull cavities 
show that they had no brains to speak of, the whole cerebral chamber 
being of about the same caliber as the tunnel for the spinal marrow. 
When, the writer discussed this subject before the British Associa- 
tion at Birmingham, and there suggested that the needs of the mech- 
anism for articulate speech would probably account for the essential 
changes in man’s lower jaw, it was pointed out by Prof. Elhot Smith 
that man’s face differs from those of his nearest congeners in many 
other particulars quite as remarkable as these. I hope some day to 
show that most of these other changes have been profoundly influ- 
enced, if not actually caused, by structural necessities demanded by 
articulate speech. ‘To attempt to do so now would take me beyond 
the scope of the present subject, and I shall therefore confine my 
attention merely to the changes that have taken place in the mandible. 
In the many endeavors that have been made to explain the why and 
wherefore of the chin, the argument as to its being due to sexual selec- 
tion deserves most notice. It has’ been rightly said that the chin is 
essential to the beauty of the human countenance, and therefore in a 
choice of mates, those deficient in this direction would be losers in 
life’s race. Arguments from esthetics are very difficult to handle, 
because of the extraordinary differences in the standards of beauty, 
not only among different species of the lower animals, but among dif- 
ferent nearly related races of men. Who can doubt that among the 
anthropoid apes there is a type of apish beauty (including the retreat- 
ing lower jaw) which satisfies the most critical and exacting simian 
taste in choosing a mate? We need not do more than allude to the 
