The =palatine bones= (Ossa palatina) are situated on either side of the posterior nares, and form the posterior margin of the hard palate. Each is twisted so as to form a horizontal and a perpendicular part. The =horizontal part= (Pars horizontalis) is a narrow plate which forms the posterior part of the hard palate. It presents smooth =nasal= and =palatine surfaces=. The =internal border= meets its fellow at the median palatine suture, on the nasal aspect of which is the nasal crest. The =anterior border= joins the palate process of the maxilla at the transverse palatine suture, and forms with it the anterior palatine foramen. The =posterior border= is concave and free; it gives attachment to the aponeurosis of the soft palate. The =perpendicular part= (Pars perpendicularis) is more extensive and forms the outer boundary of the posterior nares. The =nasal= or =internal surface= is in the greater part of its extent concave and smooth; it is marked by a narrow rough area to which the pterygoid bone is attached. Below this the bone curves outward, forming the pterygoid process. The =maxillary= or =external surface= (Facies maxillaris) presents three areas for consideration. The largest articulates with the maxilla; it is rough and is crossed by a groove which enters into the formation of the palatine canal. Behind this is a smooth part which assists in forming the =pterygo-palatine fossa=. The rough area below this is overlapped by the pterygoid process of the sphenoid bone. The =superior border= is perforated by the =sphenopalatine foramen=. Behind the foramen the two plates of the bone separate to inclose part of the =sphenopalatine sinus=. The inner plate curves inward to articulate with the vomer. The outer plate joins the maxilla and frontal and the orbital wing of the sphenoid. =Development.=—The palatine bone ossifies in membrane from a single center. THE PTERYGOID BONES The =pterygoid bones= (Ossa pterygoidea) are narrow, thin, bent plates, situated on either side of the posterior nares. Each has two surfaces and two extremities. The =internal surface= is smooth, and forms part of the boundary of the posterior nares. The =external surface= articulates with the palatine, vomer, and sphenoid, concurring with the last in the formation of the =pterygoid= or =Vidian canal=. The =anterior extremity= is free, turned slightly outward, and forms the =hamulus=, a pulley around which the tendon of the tensor palati muscle is reflected. =Development.=—The pterygoid ossifies in membrane from a single center. THE NASAL BONES The =nasal bones= (Ossa nasalia) are situated in front of the frontal bones and form the greater part of the roof of the nasal cavity. They have an elongated triangular outline, wide behind, pointed in front. Each presents two surfaces, two borders, a base, and an apex.