456 HENRY C. TRACY 



fluent with the posterior part of the bone around to the saccular 

 cavity; it extends horizontally and ends in a crescent-shaped 

 margin, forming part of the floor of the lateral recess which will 

 be described later. The upper plate of bone is divided into two 

 laminae; it extends backward, upward, and outward from the lat- 

 eral surface of the bulla itself. From its shape it may be des- 

 ignated as the falciform process. It is continuous in front with 

 the lateral wing of the prootic, with which it makes a round open 

 angle; its posterior edge is free; its dorsal edge misses reaching the 

 pterotic bone by a very narrow interval (pi. 2) which, in the fresh 

 skull, is bridged over by the lateral mass of cartilage retained 

 from the primordial cranium (fig. 8). From the under surface 

 of this process, forming with it a rounded angle along its line of 

 origin, the lower lamina of bone is given off; this may be called 

 the inferior lamina of the falciform process (ILF). Posteriorly, 

 this lamina articulates with a plate of bone from the pterotic, 

 but, below, is free and curved so as to resemble half of a low 

 broad arch (fig. 4). Between the two laminae are included the 

 inferior end of the anterior semicircular canal and its ampulla. 



Anterior to the osseous capsule, the prootic extends forward 

 to articulate with the ahsphenoid. Near the center of this part 

 of the bone is a deep notch (fig. 6), which extends down to the 

 rounded surface of the bulla, and which, when articulated with 

 the ahsphenoid, forms the foramen for the exit of the trigemino- 

 facial nerve complex. 



The anterior or orbital surface of the prootic is formed by the 

 smooth surface of the osseous capsule surrounded by projecting 

 bony processes in such a way as to form a broad shallow fossa 

 (ganglionic fossa). The capsule retains its spherical form; the 

 bony processes around it have the appearance of being molded 

 on to it. The fossa contains the ganglia of the trigeminofacial 

 complex. Inferiorly, a sharply projecting ridge separates the 

 orbital from the ventral surface of the skull. Medially, a pillar 

 of bone bo'Unds this surface and forms the lateral margin of the 

 opening of the eye-muscle canal. A deep recess extends from the 

 fossa behind the pillar; from this recess the ramus palatinus VII 

 gains access to the eye-muscle canal (fig. 8, RP VII), through a 



