54 



NEW YORK STATE MUSEUM 



process, concave in front, convex posteriorly, which touches by its 

 apex the maxillary bar [fig. 19]. 



At the posteroexternal margin of either lacrymal there is always 

 to be found a free " accessory piece " consisting of a small osseous 

 scale, horizontally attached to the bone by semiligamentous tissue. 



The lacrymal of Circus is a thoroughly pneumatic bone, and 

 presents for examination several confluent foramina, which open on 

 its inner aspect at the junction of the superciliary and descending 

 processes. 



The anterior border of the superior half of the ethmoid is broad, 

 flat, and somewhat thickened, and this part of the bone reaches 

 forward beyond the aliethmoid plates, to form a substantial base 

 upon which the frontals and premaxillary rest. Anteriorly, the 

 lower margin of the ethmoid is sharp where it joins with the 

 rostrum. 



The aliethmoid plate is conspicuous on lateral aspect of the skull. 

 Its posterior surface looks upward, backward, and outward, the 

 plane being reversed for the anterior surface. In outline it is an 

 oblong plate, which is quite true for its lower and free end, while 

 the opposite end is broader and merges with the mesethmoid. At 

 its superior and inner angle, just beneath the frontal, it is pierced 

 by an elliptical foramen for the passage of the olfactory nerve ; 

 beyond, it develops a small bony canal for its further protection. 

 The interorbital septum presents near its middle one large, ellip- 

 tical vacuity, with the major axis of the ellipse about parallel 

 with the zygomatic bar. In the recess of the angle between this sep- 

 tum and the frontal bone, we find the double groove for the lodg- 

 ment of the olfactory nerve, the grooves commencing directly in 

 front of the olfactory foramen, running parallel with each other 

 quite up to the opening for their passage through the aliethmoidal 

 plate. The zygomatic or jugal bar is very slender in Circus, and 

 the sutures of its original elements are quite obliterated. Its quad- 

 rate end develops at right angles a peglike process, to articulate in a 

 corresponding pitlet in that bone. The maxillary or anterior ex- 

 tremity has already been sufficiently described. Its relations with 

 the palatines and maxillopalatines are well shown in figures 19 and 

 21. 



The superior margin of the orbit is rounded, but as this proceed^ 

 backward it soon becomes sharp, a condition it retains to the very 

 tip of the sphenotic process, 



