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

360

The Philippine Journal of Science

1938

Below the subopercle and mostly covered by it is the most
posterior and outermost branchiostegal (Plate 2; text fig. 1,
39). There are four branchiostegals on each side, gradually
diminishing in breadth and becoming more pointed mesially.
They are all flat, thin, and lamellate. The two inner elements
are attached to the lower half of the outer face of the ceratohyal (35), the two outer bones, to the same region in the epihyal.
The elements of the opercular series grade off regularly into
the subopercle and opercle, while the preopercle and interopercle
seem not to fit in it.
Hyobranchial series (Plates 2 and 5).-There is no mistaking
the hyoid portion of the hyobranchial series, because it is the
most anterior in position and much stouter in structure than the
rest.
The glossohyal (Plates 2 and 5, 37), forming the framework
of the tongue, projects forward from the median region of the
hyoid, immediately between the closely articulated two-layered
hypohyals (36). It is mainly cartilaginous, but the posterior
half is covered by a thin membrane bone which extends a little
backward, covering the anterior portion of the 1st basibranchial.
There are two sets of hypohyals (Plates 2 and 5, 36), one on
top of the other. The dorsal parts are roughly circular in form
and smaller in size than the ventral set.
The ceratohyal (Plates 2 and 5, 35) extends backward and.outward from the hypohyals, followed still more posteriorly by
the epihyal (Plates 2 and 5, 34) which is in length roughly only
one-half the ceratohyal. The most posterior tip of the epihyal,
a little nearer the dorsoposterior border, bears a small nodule of
cartilage, the interhyal (Plates 2 and 5, 33), which articulates
the ventral half of the hyoid arch with its dorsal half, the hyomandibular.
The large urohyal (Plates 2 and 5, 38) articulates with the
posterior median portion of the hypohyals. Posteriorly it comes
in close contact with the anterior border of the clavicular parts
of the pectoral girdle, in such an intimate manner that its dorsal ridge merges gracefully into the median ridge formed by
the clavicles (56).
There are three basibranchials (Plate 5, 40), the 1st and 2d
of about equal size, and the 3d the largest of them all. A small
flake of bone develops over the cartilage in the posterior half of
the 1st basibranchial (Plate 5, 40,), partly covering the anterior
portion of the 2d. The 2d basibranchial (Plate 5, 402) possesses
a similar flake of bone in the same region as the 1st, which in