A morphometric study of the posterior cranial fossa was made in a series of 100 Chinese adult cranial bases at random. According to the level of the superior margin of the transverse sulcus ok two halves of the fossa

three types of posterior cranial fossa were classified

that is

the left high type

the equal high type

and the right high type. Variables studied

20 in sum

including the depth

the sagittal and transverse measurements

and distances between the endocranially situated osseous points about the fossa. Each sagittal measurement represents approximately the antero-posterior distance of the medial

middle

and lateral thirds of that half of the fossa respectively

and each transverse measurement represents almost the width of the anterior

middle

and posterior thirds respectively.Statistical analysis revealed that most of the metric valuts on the right half of the fossa are greater than that of the left one

and the side difference of S1 and S2 measurements between two halves is highly significant. Secondly

the mean values of all transverse measures of the left half are greater in the total sample

and T3 measurement is even greater in each type of the fossa. Thirdly

the differences of all measures between the types mentioned above are mostly none significant. From these results

it is reasonable to conclude that asymmetry

between two halves of the posterior cranial fossa does exist virtually

and

in general

the right half of the fossa is the larger