DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 243 
nerve has no maxillary bridge over it at present. The lachrymal (/.) has a large, 
pentagonal facial plate ; its thick orbital margin is somewhat notched, and inside that 
notch is the canal; the thickness of the orbital margin, which helps the frontal 
and jugal to give finish to the orbital ring for nearly three-fourths of a circle, is so 
large as to hide the interorbital plate of the bone and its canal. 
Lying between the aberrant Tupaia and the typical Hrinaceus, this type tends to 
finish its orbital ring, especially in the perfection of the supraorbital rim of the 
frontal; there is, however, no free postorbital process, the ribbed edge merely runs 
back and binds upon the parietal. The frontal is perfect in the upper half of the huge 
orbital cup, but unfinished, behind; yet giving promise of the Lemurine orbit—a 
promise fulfilled in Zupaia, soon to be described. 
Behind that very extensive hollow, thin orbital plate, the parietal (p.) just comes in 
and divides it from the squamosal ; the rest of the parietal is seen to be convex above, 
and gently pressed inwards over its lower edge, which has two large shallow emargi- 
nations ; the one, in front, over the squamosal, and the other, behind, over the huge 
auditory capsule. The triangular interparietal (7.p.) is sinuously united to the parietal 
above, and hooks round its rounded hinder margin, lower down. From the middle of 
the lower edge of the parietal to the lachrymal the outworks of the skull are completed 
by two bones, the squamosal (sq.) and the jugal. The latter bone (j.) is strong for an 
Insectivore; it protects the maxillary nerve (V*.), wedges into the lachrymal and 
maxillary, is grooved and broad in front, outside, and ends as a blunt style below the 
jugal process of the squamosal, some distance in front of the glenoid facet (g/.c.). The 
squamosal (sq.) just rests its spike upon the jugal, and then broadens out into the 
glenoid tract, which is covered with a subconvex oval cartilage looking inwards and 
somewhat forwards (see fig. 2, gi.c.), and into the oval, hollowed, temporal plate, 
which overlaps more than half of the lower edge of the parietal. The jugal spike 
runs into the thick outer part, whose upper edge is sharp and sinuous, first convex 
and then concave, where it runs up and meets the squamous or temporal edge. The 
lower margin has two concavities, the glenoid, and tympanic, and two processes, the 
post-glenoid and the post-temporal, the latter is the larger of the two; under these 
we just see the tympanic annulus (a.ty.). 
The mandible (d.) is scarcely developed into distinct processes, behind ; the coronoid 
(c.p.) being very low; the rounded condyloid process (cd.p.) is separated by a 
rounded notch from the small, sharp, angular process (ag.p.); the ramus, with its 
swollen alveolar space, and teeth just cutting the gums, is gently convex, below, and 
with a slightly arcuate outline runs forwards to its narrow, pointed fore end. 
In the palatal view (fig. 2) there seems nothing, at first, to remind one of the Mar- 
supial ; in this, Rhynchocyon agrees with the two types next to be described, namely, 
Galeopithecus and Tupaiu, The general form of the palate is roughly oval, but emar- 
ginate at its narrow, fore end, and having a broken or dentate hind margin. ‘The 
premaxillaries ( pa.) are of short extent, being largely overlapped by the maxillaries 
21 2 
