The Philippine journal of science. [Vol. 67, no. 1]

354

The Philippine Journal of Science

1938

bears the posterior half of the articulating surface of the hyomandibular. Of all the elements of the cranium, the pterotic
articulates with the most bones. Anterodorsally it meets the
frontal and the parietal; dorso- and ventromedially, the epiotic;
ventromedially, the exoccipital; anteroventrally, the sphenotic;
ventrolaterally, the prootic (15) and exoccipital; and posteroventrally, the opisthotic.
The opisthotic (Plate 1, 10) is a small bone applied closely
to the ventromedial region of the pterotic spine of each side. It
meets the epiotic dorsally and the exoccipital medially. This
bone is easily removed with the removal of the posttemporal,
the tip of its opisthotic limb being well joined by fibrous connections with the opisthotic.

a2? e 39
EI. 1. Skull, left lateral aspect; X 1.5. 4, Frontal; 16, hyomandibular; 21, mesopterygoid;
22, metapterygoid; 23, preopercle; 24, opeicle; 25, subopercle; 26, interopercle; S7, articular; 29, angular; 30, dentary; 31, maxillary; 32, premaxillary; 39, branchiostegal; 47,
supraorbitals; 48, preorbital; 49, suborbitals; 50, postorbital; 51, nasal; 52, supratemporal;
53, subtemporal; sup cr, supraoccipital crest or spine.

The remaining portion of the brain-case backwall is formed
by the exoccipital (Plate 1, 11) bones which lie closely together
along the median line, immediately below the supraoccipital.
The bone on each side is prolonged into a pointed plate which
slopes upward and backward, and meets the other plate in the
median line, forming a roof which fits over the neural arch of
the first vertebra. It affords a safe protection for the hind
portion of the brain and the immediately succeeding portion of
the spinal cord. The anterodorsal wing of the bone, as stated