190 
ME. W. K. PARKER OX THE STRUCTURE AND 
Over it is seen the large, smooth supraoccipital, and below it the flattish condyle 
(< oc.c .). 
At the fore part of the mastoid tract the epihyal and facial nerve ( e.hy ., YII.) are 
shown in relation, and the 9th, 10th and 12th nerves are figured as they escape 
from the skull. There is still a considerable tract of cartilage between the supra¬ 
occipital, exoccipital, prootic, and opisthotic bones. 
The upper view of this rapidly growing skull is shown in fig. 6 ; without the long 
cartilaginous snout ( al.n .) this view would have been very imperfect. That finishes 
this long, flattened, boring, wedge-shaped skull. Eight pairs of investing bones, and 
one single pair—the interparietal—finish the upper and lateral parts of the skull; they 
are so developed and imbricated as to increase their general breadth up to the auditory 
region, and then the skull ends in a somewhat irregular semicircle, not perfected 
by any superficial bone, but by ossification of the walls and roof of the cliondro- 
cranium ( s.opr.o'.). 
A lower view (Plate 27, fig. 5), with the tympanies and ossicula removed, shows the 
great progress in ossification and general development that have taken place, whilst 
the young Mole has rapidly become twice as heavy as it was when only 3 inches long 
—the last stage. The dentigerous semicircle formed by the premaxillaries ( px .) with 
their long palatine processes (p.px.), largely hidden by the maxillaries (mx.) is followed 
by the long sinuous dentary line of the maxillaries; several of the molars are only 
just cutting the gums with their sharp cusps. The palatine plate formed by the 
palatine bones (pa. ) is shorter and wider than that formed by the maxillaries, for the 
suture between the two pairs of bones is very far forward ; the Mole has a very per¬ 
fect and normal hard palate. The openings of Jacobson’s organs (j.o.) are seen in the 
anterior palatine foramina, and the posterior foramina are large and wide apart, they 
are in the line of the lateral suture between the palatines and maxillaries. The 
palatine plates of the palatines have a beaded edge, and this thick or limbate margin, 
which turns inwards and backwards to form the wall of the nasopalatine canal behind 
the hard palate, is, altogether, bracket-shaped. The palatines go twice as far back on 
their palatine plate, and are very solid and spongy where they embrace and support 
the base of the skull. On to them, the pterygoids ( pg .), are articulated, and they also 
have a pedate expansion above, supporting the skull; their hamular process is not 
quite ossified (pg.c.). The presphenoid (p.s.) is a long beam of bone, formed by fusion 
of the orbitosphenoids, and separated by a considerable synchondrosial tract from the 
basisphenoid (b.s.) ; this latter is a truly marvellous bony centre, and as far as my 
experience goes is, in this creature, relatively wider than in any other type. In this 
aspect, the basisphenoid runs across the whole basal region up to the floor of the 
orbits, so that very little of the top of the skull can be seen right and left. 
The fore edge is narrower than the hind margin ; both are sinuous, and the outer 
margin is rounded, and almost semicircular. The anterior third, which is clamped 
by the cranial plates of the pterygoids, has its floor perfect, but the bone is burrowed. 
