The =lacrimal bones= (Ossa lacrimalia) are situated at the anterior part
of the orbit, and extend forward on the face to the posterior border of
the maxilla. Each presents three surfaces and a circumference.
The external aspect is clearly divided into orbital and facial parts by
the orbital margin. The =orbital surface= (Facies orbitalis) is
triangular in outline, smooth and concave; it forms part of the inner
and front wall of the orbit. Near the orbital margin it presents a
funnel-like =fossa= for the lacrimal sac (Fossa sacci lacrimalis), which
is the entrance to the osseous lacrimal canal. Behind this is a
depression in which the inferior oblique muscle of the eye takes origin.
The =facial surface= (Facies facialis) is more extensive, and has the
form of an irregular pentagon. It is slightly convex and smooth in the
foal, flattened in the adult. It usually bears the small =lacrimal
tubercle=, situated nearly an inch (ca. 2 cm.) from the orbital margin.
The =nasal= or =internal surface= (Facies nasalis) faces into the
frontal and maxillary sinuses. It is concave and very irregular, and is
crossed almost horizontally by the =osseous lacrimal canal= (Canalis
lacrimalis osseus).
The =orbital margin= (Margo orbitalis) is concave, rough above, smooth
below.
The =circumference= articulates above with the frontal and nasal bones,
below with the malar and maxilla, in front with the maxilla, and behind
with the frontal. The various sutures so formed are designated by
combinations of the names of the bones.
=Development.=—Each ossifies in membrane from a single center.