OF DIDELPHYS VIRGINIANA. 59 



terminate in a point, which falls short of the end of the jaw ; ^^ rostral " hones ;ire not 

 developed. 



The ascending ramus of the mtermaxillary is wedged in hetween the nasals and 

 maxillaries, extending ahout an inch npon the cheek, overriding the side of the nasal, 

 and being in turn overlapped by the maxillary. The rami are curved, with the convexity 

 outward, at first divaricating from each other to increase the calibre of the nasal aper- 

 ture, and then somewhat approximating, and also each curling upon itself, as the alveolar 

 borders come to meet on the median line in front. The palatal plate of each bone is 

 almost divided into two longitudinal parts by an extensive fissure — the incisive foramen — 

 which nearly reaches the alveolus. This foramen is not completed behind by the intermax- 

 illary ; it is simply a slit, so fiir as tliat bone is concerned. The median moiety of the 

 palatal plate is an extremely long and attenuated spicula whose extent is not visible from 

 below in tlic articulated skull, as the palatal plate of the maxillary overlaps it. The lateral 

 moiety is much shorter, as well as broader ; it terminates at the anterior border of the 

 socket of the upper canine. The intermaxillarics are never confluent witli each other or 

 with surrounding bones. Each contains five teeth. 



The maxlUari/ is large, and has numerous strong processes. Its surface is smooth; 

 the foramen appears just above the first or second premolar, opening upon a slightly 

 depressed space, in advance of wliich is the bulging that denotes the insertion of the 

 great canine. The nasal plate or process curves toward the nasal bono, and unites with 

 the latter for about half its length, being anteriorly cut off by tlic intermaxillary; the poste- 

 rior prolongation of this plate, in tlie form of a sharp pointed process, reaches the frontal. 

 A deep excavation in the border of the bone, just below the process, indicates the seat of 

 the lachiymal. Posteriorly the bone sends upward a large, stout, zygomatic process, for 

 union with the malar, in a manner to be more particularly noticed under liead of tlio latter. 

 The alveolar border is strongly developed, particularly behind ; it narrows anteriorly, and is 

 deficient at the wide interspace between the first and second premolars. The pahital plate 

 or process meets its fellow along a perfectly straight median line. Besides being nicked an- 

 teriorly to perfect the incisive foramen, it is deficient posteriorly, where the palatal plate of 

 the palatine completes the bony roof of the mouth; and is, moreover, deeply fissured to form 

 the posterior elongated vacuity, described below. Both upper and under surfaces of the 

 palatal plate are nearly smooth ; on the latter, however, a shallow but distinct groove may 

 be observed running from the posterior fissure to the root of the canine. The posterior bor- 

 der of the bone, between the malar and palatine, is thick, smooth and concave ; it is con- 

 tinued as a process just behind the last molar, taking part in the formation of the most 

 postero-external of the ten openings in the bony palate. The share that the zygomatic 

 process takes in the formation of the outer wall of the orbit is inconsiderable, though greater 

 than appears on viewing the bone from the outside. The floor of the orbit — what little 

 there is of it — is maxillar. The surface of this part of the bone is traversed by a groove, 

 in which lies the maxillary division of the trigeminus, which is conducted by this means 

 along the orbital floor into a bony canal, whose outlet is the maxillary foramen. The bone 

 bears upon the inner surface of its ascending plate, the lower or anterior turbinal bone — a 

 spongy convoluted mass, of extremely delicate texture, which nearly fills that part of the 

 nasal chamber not occupied by the ethmo-turbinal. The maxillary is permanently distinct 

 from all of its surroundings. The alveolus bears eight teeth 



