OF THE SOUTHERN APTERYX. 285 
Of the bones more immediately concerned in the formation or motion of the jaws, 
that element of the temporal may be first described which in birds is always moveable 
and articulated at once with the cranium and both the upper and lower jaws. 
The tympanic bone is of a subcompressed trihedral form, and sends forwards into the 
orbit a longer and slenderer process than in the larger Struthionide: its upper arti- 
cular surface is a transversely extended convex condyle, which plays in a corresponding 
cavity internal to the base of the zygomatic process. The opposite extremity is ex- 
panded, and presents two distinct articular convexities for the lower jaw, the inner one 
being the largest : above the external convexity there is a small but deep depression for 
the reception of the deflected extremity of the jugal bone. 
The posterior extremity of the pterygoid bone is securely wedged in between the or- 
bital process of the tympanic and the tranverse process of the sphenoid : as it advances 
forwards it expands, as in the other Struthionide, into a thin plate of bone, which is 
bent upon itself with its concavity turned inwards, and is continued by anchylosis into 
the palatine bones, so that the limits between them cannot be defined. 
The palatine bones are in like manner confluent with the maxillaries. They are pierced 
by two narrow elliptical posterior nasal foramina, about 3 lines in length, over which 
the exterior margin of each palatine bone arches from without inwards, and these over- 
arching lamine gradually approximate, as they advance forwards, and meet about one 
inch anterior to the nasal foramina, from which an imperforate plate of bone, impressed 
with a narrow median fissure, and composed of the confluent palatal processes of the 
maxillary and intermaxillary bones, is continued to the end of the beak. The limits 
between maxillary and intermaxillary bones are indicated by two fine oblique lines, com- 
mencing at the outer margin of the roof of the mouth, about 23 inches from the apex 
of the beak. 
The jugal style, which in the Ostrich may be separated in the full-grown bird into 
a zygomatic and malar portion, consists in the Apteryx of a single slender com- 
pressed twisted bone, anchylosed with the maxillary bone in front, and terminated be- 
hind by an obtuse deflected extremity, which is received into a corresponding vertical 
cavity in the upper part of the outer process of the tympanic bone. By this mode of 
attachment the tympanic bone offers increased resistance to the pressure transferred to it 
by the lower jaw, at the same time that it gives additional strength to the upper mandible. 
It is continued backwards in the same line with the upper maxillary bone as in other 
Struthionide, and is not bent downwards at its junction with the maxillary as in the 
Ibis and other Graile. 
The superior macillary bone presents the singular form of a nearly perfectly flat 
elongated triangular plate of bone, which is imperforate, and is continued by unin- 
terrupted ossification with the intermaxillary. The Rhea among the Struthionide 
makes the nearest approach to the Apteryz in the structure of this part of the skull; 
but the maxillary plate is perforated by large foramina, and sends upwards on each 
