No. 424.] DIVISION OF THE MALAR BONE. 285 
This fissure, as the bone grows, gradually closes at its proximal 
extremity, but becomes extended, by the new bone, at its distal 
end. The result of this is that even as late as at the birth of 
the human foetus the parietal bone shows a more or less marked 
posterior, and rarely also an anterior, partial division, exactly 
analogous with, it seems to me, though almost generally less 
persistent than, the malar incisures. The parietal division may 
persist even up to adult life and then the analogy between the 
same and a malar incisure is still closer. The difference 
between this form and a complete division (or a remnant of 
such) in either the parietal or the malar is that in the simple 
incisure and fissure we have before us only a retardation of the 
union of the distal portions of the original segments of the 
bone, while in the complete division (or its remnant) we are 
confronted with a case of a complete non-union and separate 
development of these segments. The two effects may be pro- 
duced, and probably are produced in such a case as that in the 
Peruvian skull with a complete malar division on one and two 
incomplete ones on the other side, by different degrees of the 
same cause ; nevertheless they cannot be considered identical. 
The cause which induces a separate development of all or 
some of the centers of ossification of a bone must be potent 
and be present extremely early ; a persistence of a fissure might 
be due to a weaker cause of the same nature, but possibly also 
to later causes of differing kind. The complete divisions deserve 
fully the term “anomalies,” or “atypical formations," while the 
partial divisions come more under the category of developmental 
defects or retardations. 
The partial malar divisions are not attended by similar con- 
ditions in other bones of the skull. They also do not seem to 
stand in any relation with the metopic division ; specimens 
with the frontal suture in my Peruvian series have, upon an 
additional inspection, shown no greater. percentage of malar 
incisures than other skulls in the same collection. 
There is nothing in the appearance of the partial divisions, 
except, perhaps, their size, which would allow us to differentiate 
them from remnants of complete malar sutures. Should a 
division extending beyond the middle of the bone be found, it 
