Bauhaus-Universität Weimar

Titel:
The Cyclopaedia of Anatomy and Physiology, vol. 3: Ins-Pla
Person:
Todd, Robert Bentley
PURL:
https://digitalesammlungen.uni-weimar.de/viewer/image/lit29464/281/
MARSUPIALIA. 
Skelete der Bcutelthiere ; a small proportion of 
their bony circumference is due to the anterior 
extremity of the palatal process of the maxil¬ 
lary : the same structure obtains in the Wom¬ 
bat, Koala, and Opossums. In the Dasyures 
and Phalangers a greater proportion of the 
posterior boundary of the incisive or anterior 
palatal foramina is formed by the maxillaries ; 
in the Petaurists they are entirely surrounded 
by the maxillary bones, while in the Perameles 
they are, on the contrary, entirely included in 
the intermaxillaries. They always present the 
form of two longitudinal fissures : the Myrme- 
cobius agrees with the other Marsupials in this 
structure. 
The superior maxillary bone in the Wom¬ 
bat sends upwards a long, narrow, irregular 
nasal process, which joins the frontal and 
nasal bones, separating them from the inter¬ 
maxillaries ; the part of the maxillary bone 
which projects into the temporal fossa behind 
the orbit presents two or three smooth tuberosi¬ 
ties, formed by the thin plate of bone covering 
the pulps of the large curved posterior grinders. 
The corresponding part in the Perameles lagotis 
is perforated by numerous minute apertures 
like a cribriform plate, and this structure is 
presented in a slighter degree in the Potoroos 
and Ursine Dasyure. The antorbital foramen 
does not present any marked variety of size, 
which is generally moderate. It is much 
closer to the orbit in the carnivorous Marsu- 
pialia than in the corresponding placental 
quadrupeds. It is relatively largest in the 
Ursine Dasyure. It presents the form of a 
vertical oblique fissure in the Wombat. I have 
observed it double in the Kangaroo. The chief 
differences in the maxillary bones, indepen¬ 
dently of the teeth and their alveoli, are pre¬ 
sented by the palatal processes, the modifica¬ 
tions of which we shall consider in conjunction 
with those presented by the palatal processes 
of the palatal bones. The perforations and 
vacuities of the bony palate deserve, indeed, 
particular attention, as they are often specific 
and of consequence in the determination both 
of recent and fossil species. 
In Phalangista Cookii, in Petaurus fiaviven- 
ter, and Petaurus sciureus, in Macropus major, 
and some other great Kangaroos the bony 
palate is of great extent and presents a smooth 
surface, concave in every direction towards the 
mouth ; it is pierced by the two posterior palatine 
foramina at the anterior external angles of the 
palatine bones, either within or close to the 
transverse palato-maxillary sutures. Behind 
these foramina, in the Kangaroo, there are a 
few small irregular perforations. The bony 
palate is similarly entire in the Hypsiprymnus 
ursinus. In Macropus Bennettii there are four 
orifices at the posterior part of the bony palate. 
The two anterior ones are situated upon the 
palato-maxillary suture, and are of an ovate 
form with the small end forwards. The two 
posterior foramina are of a less regular form 
and smaller size. In the Brush Kangaroo 
(Macropus Brunii, Cuv.) the posterior palatal 
foramina present the form of two large fissures 
placed obliquely and converging posteriorly. 
VOL. HI, 
They encroach upon the posterior borders 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. In Hyps, setosus they extend as far for¬ 
wards as the interspace between the first and 
second true molars; in Hyps, murinus they 
reach to that between the second and third 
true molars. Posterior and external to these 
large vacuities there are two small perforations. 
In the Phalangers, with the exception of P/i. 
Cookii, 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 pos¬ 
terior 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 pro¬ 
cesses of the palatine bone extend as far for¬ 
wards in the median line as the third molars : 
a long and narrow fissure 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 Ursine Dasyure a large transversely 
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,* perhaps in young- 
skulls wholly, bisected by a narrow longitu¬ 
dinal osseous bridge. In Mauge’s Dasyure there 
are two large ovate apertures crossing the palato¬ 
maxillary sutures separated from each other 
by a broad plate of bone ; posterior to these 
are two apertures of similar size and form, 
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 to 
the fourth and fifth grinders ; the posterior 
margin of the bony palate has four small aper¬ 
tures on the same transverse line. 
Now there is no. carnivorous quadruped in the 
placental series which has a bony palate cha¬ 
racterized by perforations and vacuities 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 suture. The very great in¬ 
terest which is attached to the fossil remains of 
the Stonesfield Marsupials, the only mammi- 
* The large aperture in the skull of the Da- 
syurus ursinus figured by Temminck is the result 
of accidental injury to the bony palate. Monq-i 
graphies de Mammalogie, pi, viii. 
T
        

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