OF THE MARSUPIALIA. 389 
encroach upon the posterior border of the maxillary plate. Anterior to these vacancies 
there are two smaller foramina, and posterior to them are one or two similar foramina. 
In the Australian Potoroos', Wombat* and Koala’, the posterior palatal openings are 
large and oval, and situated entirely in the palatal bones; posterior, and external to 
these, there are two small perforations. In the Phalangers (Phal. Cookii excepted) the 
palatal openings are proportionally larger ; they extend into the palatal process of the 
maxillaries, and the thin bridge of bone which divides the openings in the Potoroo, &c., 
is wanting: the two perforations at the posterior external angles of the palatine bones 
are also present. In the Virginian Opossum the bony palate presents eight distinct 
perforations, besides the incisive foramina: the palatal processes of the palatine bone 
extend as far forwards in the median line as the third molares: a long and narrow fis- 
sure extends for an equal distance (three lines) into the palatal processes both of the 
palatines and maxillaries. Behind these fissures, and nearer the median line, are two 
smaller oblong fissures ; external, and a little posterior to these, are two similar fissures, 
situated in the palato-maxillary suture ; lastly, there are two round perforations close to 
the posterior margin of the bony palate. In the Thylacine* the two posterior palatal 
vacuities are an inch in length and half an inch in width, exposing to view the convo- 
lutions of the turbinated bones of the nasal cavity. In the Ursine Dasyure’ a large trans- 
versely oblong aperture is situated at the posterior part of the palatal processes of the 
maxillary bones, and encroaches a little upon the palatines ; this aperture is partly, per- 
haps in young skulls wholly, bisected by a narrow longitudinal osseous bridge*. In 
Dasyurus macrourus’ two large ovate apertures, situated in the palato-maxillary sutures, 
are divided by a broad plate of bone; posterior to these are four similar but smaller 
apertures, which, being situated nearer the mesial line, are divided by a narrower 
osseous bridge ; each posterior external angle of the bony palate is also perforated by 
an oval aperture. In the Viverrine Dasyure* the two vacancies which cross the palato- 
maxillary suture are in the form of longitudinal fissures, corresponding in situation with 
the penultimate and antepenultimate grinders; the posterior part of the bony palate 
is perforated by several small apertures. Now there is no carnivorous quadruped, 
in the placental series, which has a bony palate characterized by perforations and vacu- 
ities of this kind. In the Dog, the Cat, and the Weasel tribe, the bony palate is only 
perforated by two small oblique canals, which open in or near the palato-maxillary su- 
ture. The very great interest which is attached to the fossil jaws of the Stonesfield 
Didelphys,—the only mammiferous remains hitherto discovered in the secondary forma- 
tions, will justify the minuteness with which I have dwelt on characters that, inclusive 
of the teeth, serve to distinguish the cranium of the Opossum from that of any placental 
quadruped. 
1 PLLXXI fig.4.  * Jb fig.1. 3 PL LXIX.fig.3. * PLLXX.fig.1. > PL LXX. fig. 5. 
6 The large aperture in the skull of the Dasyurus Ursinus, figured by M. Temminck, is the result of accidental 
injury to the bony palate——Monographies de Mammalogie, Pl. VIII. 7 Pl. LXX. fig.3.  * Pl. LXX. fig. 2. 
