O4 MR. W. K. PARKER ON THE STRUCTURE AND 
Jugal, the optic hole (II.) can be seen, The temporal region of the frontal is gently 
marked off from the orbital, and here a large triradiate suture can be seen; it is formed 
by the squamosal runuing backwards and forwards from the coronal suture ; both of 
these are very long seams. 
The coronal suture rans downwards and forwards, and the squamosal backwards 
and downwards; these plates of bone, thus stitched together, swell towards the 
temporal space aud muscle, and that space is but little enclosed, outwards, by the 
stunted zygomatic process of the squamosal. Over those parts the parietal forms 
a larger front, and a lesser hind, convexity, and ends against the supraoccipital in 
a straightish line—halt the lambdoidal suture (see fig. 4). The squamosal is two- 
thirds the size of the parietal ; it is a roughly oval plate, narrowing backwards. 
Before and behind its edge is fretted away, or toothed, below ; between its ends 
the bone grows outwards, swelling behind into an air-cavity of unusual size, in front 
it grows out into the condyle and small zygomatic spur (gl.f.). 
Under the notched fore edge we see the alisphenoid standing out from the 
orbitosphenoid, and between the two sphenoidal fissure (V!.). Close under and 
behind this notch the enclosed foramen rotundum (V*.) is seen, and peeping out 
between the lower edge of the squamosal and the upper edge of the pterygoid (pgq.) 
the foramen ovale (V*.). 
Between the latter rough, hollow bone, and the last tooth-socket (m.), we see the 
edge and ascending part of the limited palatine (pa.). 
The annulus, manubrium, and membrana tympant (a.ty., m.ml.) come into view 
under the postglenoid part of the squamosal, and under its hinder toothed part, the 
opisthotie region (op.) with the confluent epihyal (e.Ay.), unossified, and under and 
behind the junction, the facial nerve (VII.). Just the edge of the occipital arch with 
its condyles (s.0., @.0., oc.c.) are seen in this aspect. 
The external view of the mandible (fig. 3, d.) shows what development has taken 
place since the first stage (tig. 9, d.). I spoke of the first tooth or tusk as doubtfully 
canine ; in the upper jaw, in the first stage (Plate 8, fig. 1), it is the first tooth, but in 
the lower jaw there is one in front of the rudimentary lower tusk—five in all ; it is 
very small, prematurely developed, and early lost (see Plate 9, figs. 3 and 9). Thus 
the tusk, at most, can only represent the first premolar of the normal Mammalian 
dentition. 
The coronoid process (cr.p.) is now separated by a large semicircular notch from the 
condyle (ed.p.), and that by a shallow notch from the angular (ag.p.), which is not 
very deep in this genus. 
The fore end of the mandibles is narrow (figs. 3 and 5) and the sutural symphysis 
of a considerable extent ; seen from below, the mandibles are as curiously swollen to 
form the socket of the tusk, as the face is above; the sockets of the hinder teeth are 
directed strongly inwards. Here we see how soon the dentition attects the form of the 
mandible (figs. 3 and 9), and the loss of teeth is taking place, here, before one’s eyes. 
