OSTEOLOY AND DENTITION OF HYLOMYS. 457 
equal breadth throughout, it being widest between the first and second molars. Its 
posterior margin is slightly thickened, but not nearly so strongly as in the last-mentioned 
genus. ‘The palatal suture terminates posteriorly in a very minute spine, the equivalent 
of that structure which is so strongly developed in Erinaceus; and there are indications 
of the transverse bony plate which is so well defined at the posterior margin of the 
palate of the Hedgehog. The pterygoid fossa is deep and well developed, and reaches 
forwards, even anterior to the posterior margin of the palate; and the outer plate is 
decidedly larger than the internal, and is directed outwards and slightly downwards, 
being prolonged backwards to the tympanic bulla, from which it is only separated by 
an extremely short ridge, internal to the foramen ovale. The mesopterygoid fossa is 
rather deep and narrow from before backwards, more so than in Tupaia, and less so than 
in Hrinaceus. The ectopterygoid plate is perforated externally, at its base, by two 
prominent foramina, one before the other, with an intervening arch of bone, producing 
the appearance of an incomplete canal, which is intensified by the grooved surface 
before the foremost foramen and which forms the outer margin of the sphenoidal 
fissure. The two foramina and the foramen ovale are in one line, and only separated 
from each other by narrow bony septa. One or two minute foramina open almost 
into the posterior border of the hindmost of the two foramina, which is slightly below, 
but immediately anterior to, the foramen ovale. Are these two foramina external ali- 
sphenoid canals? or is the more anterior of them the foramen rotundum? What leads 
me to believe they are the former is their direction ; for a fine wire can pass straight 
through them from before backwards from the outer surface of the cranium. If this 
opinion is correct, the foramen rotundum is merged in an enlarged sphenoidal fissure, 
which is large, and has its floor formed by the ectopterygoid and pterygoid plate of the 
palatine bone. The optic foramen is round, and separated from the inner and anterior 
margin of the sphenoidal fissure by a thin plate of bone. Below, and slightly posterior 
to the optic, is the suboptic foramen, which is even larger than the former. A fine wire 
passed through it comes out at a small foramen on the inner side of the internal opening 
of the optic foramen of the opposite side. The two foramina between the optic foramina, 
on the inner aspect of the skull, are transversely oval, rather well-marked apertures, 
much more developed than in Erinaceus; and in looking through the optic foramina 
from without they are seen beyond it. There is a minute foramen on the anterior 
margin of the optic foramen, and three venous foramina a short way above and anterior 
to it, two of which are directly above each other and posterior to the third, and lead at 
once into the cavity of the skull. Another and larger, slightly above and posterior to 
the two, and on the anterior orbital margin of the parietal and between it and the orbito- 
sphenoid, leads backwards to a short canal that opens on the internal aspect of the 
parietal, traversing it and the squamosal in the groove of the lateral venous sinus that 
communicates with the supraglenoid foramen. It opens between the parietal and 
squamosal slightly posterior to the postglenoid foramen, which is large. Anterior to 
