INSECTIVORA.
and the foramen magnum looks downwards and backwards, bnt muoh more in
the latter than in the former direction. The oondyles look outwards, forwards, and
downwards. There is a very minute rudiment of a para-oodpital process,1 and more
distinct indications of a mastoid protuberance. The meatus mditorim exterms looks
outwards and slightly upwards. The tympanic bull® are entire, and no portion of
the basi-sphenoid contributes to form them. There is a distinot basi-occipital ridge,
but it is not continuous with the well-marked ridge of the mesopterygoid fossa. A
groa.il post-glenoid process contributes to complete the anterior border of the meatus
auditorius exterum. The auditory bull® are placed obliquely across the base of
the skull, being divergent posteriorly and convergent anteriorly, in which direction
they taper to a point which is in the same line with the lateral wall of the mesopterygoid
fossa. The glenoid articular surface is almost flat, but slightly concave>
where it is overlooked by the post-glenoid process. The mesopterygoid fossa contracts
from before backwards, but its broadest diameter corresponds to the interval
between the anterior extremities of the auditory bull®. Its anterior two-thirds is
marked by a pronounced median vomerine ridge, which is partially prolonged on to
the basi-sphenoid. The ectopterygoid plate is small, pointed and falcate, and is
directed downwards, backwards and outwards, and is perforated at its base by a canal.
The pterygoid fossa is small, and is separated from the palate by a ridge of bone as
long as the longitudinal extent of the fossa. There are one or two minute circular
imperfections in the basi-sphenoid. The palatal surface is concave from before
backwards, and from side to side, and an obscure osseous ridge runs along the
median line. # .
There are a number of imperfections in the posterior third of the palatal surface.
The posterior margin of the palate is distinctly thickened, forming a ridge of more
compact osseous tissue than the rest of the palatal surface. That portion of the
margin corresponding to the mesopterygoid fossa is doubly concave from behind
forwards, each concavity corresponding to one-half of the fossa. The portion of the
margin external to this is convex from before backwards, and projects backwards
about half the diameter of the last molar beyond that tooth. The first and second
premolars are separated by a short interval corresponding to the distance, or nearly
so, that intervenes between the first and second incisors, and the canine is removed
from the second incisor by about double that distance. Viewing the skull sideways,
the alveolar margin arches upwards as far as the canine, and then, in a long, slightly
convex sweep, goes downwards as far as the posterior margin of the second molar,
beyond which it is directed upwards and inwards.
There is a rather large supra-orbital foramen at the point where the contraction
between the orbits is most marked, and a smaller infra-orbital foramen above the
second premolar. There are two small foramina placed one above the other on the
parietal above the zygoma and the meatus auditorius extemus, and both open into
the moderately large foramen behind the post-glenoid process. A similar foramen
1 Mivart did not observe one in the skulls he examined.
occurs in Eylomys and Eri/naceus. Posterior to the lowest of these foramina there
is another small foramen on the lambdoidal ridge which opens almost directly into
the skull in Tu/paia and the above-mentioned genera. There is a distinct foramen
below and internal to the mastoid process (the stylo-mastoid foramen ?) and internal
to it, and on the hinder third of the auditory bulla a small rounded foramen with
well-defined osseous walls occurs opposite to the middle of the occipital condyle, and
interrogatively mentioned by Mivart as the carotoid foramen, which it is in all probability.
Posterior and slightly external to it, and internal to the posterior extremity
of the auditory bulla and the mastoid, is a rather large foramen formed by the arching
over of the inferior external angle of the occipital to these bones, and constituting
th& foramen lacerum posterius, which is directed upwards and slightly backwards
as a short bony canal. Internal and slightly posterior to it is the anterior condyloid
foramen. Between the auditory bulla and basi-occipital there is a rather long
groove running above the carotoid foramen, forwards from the opening of the foramen
jugulare, ultimately forming a closed canal foramen lacervm cmterius between
the bulla and basi-occipital and basi-sphenoid. The foramen ovale is situated at the
middle of the anterior aspect of the bulla, and is formed externally by that bone and
the sphenoid, the former constituting the under margin of the opening. External
and slightly posterior to the foramen ovale, anterior to the base of the tympanic plate,
between the squamous and the bulla, there is a minute foramen, or rather fissure, in
the position of the fissure of Glaser. At the anterior wall of the bulla, immediately
internal to the foramen ovale and on a lower level, is a round foramen which escapes
observation unless the skull is held sideways. I t passes directly outwards and backwards,
and a fine wire passed through it comes out at the meatus auditorius extemus
in a macerated skull. The external pterygoid plate is perforated by a canal at its
base. Anterior, internal, and superior to the forward termination of this canal, is the
foramen rotv/ndum, separated by a marked interval from the sphenoid fissure which is
directed outwards, forwards and upwards, and separated from the optic foramen by a
narrow spicule of bone. There are two foramina external to the sphenoidal fissure,
the most external the being smaller. The infra-orbital foramen opens internally
at the most anterior portion of the lower angle of the orbit, and the external orifice is
0*20 of an inch in advance of it. The lachrymal canal opens rather external than
internal to the orbit below the backwardly projecting process at the anterior margin
of the orbit, above which there is also another small foramen leading into a canal
opening into the nasal cavity. The posterior palatine foramen is at some distance
external to the orbital opening of the infra-orbital foramen; and the anterior palatine
foramen is still larger.
The longitudinal ramus of the mandible has a long, gentle, downward and
upward curve as far forwards as the second premolar, anterior to which the alveolar
border shows a slight downward curve. The dental portion of the jaw is laterally
compressed, but the portion at the base of the ascending ramus is contracted, and
more or less rounded. The coronoid process is directed upwards and backwards, and
its posterior margin overlooks the condyle, from which it is distinctly removed, the
p,