DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 249 
rounded manner ; the paroccipital ridges of the exoccipitals are scarcely marked, and 
the supraoccipital (s.o.) is gently convex. The basioccipital (b.0.) is large, and 
through the bulging of the bony sheath of the notochord (cephalostyle), subcarinate 
in front, below. The condyles (oc.c.) are large and obliquely reniform, and there 
is, besides these, much cartilage still left between the bony centres of the arch ; 
the foramen magnum (f1m.) is very large, and pyriform in shape. 
The ossicula audittis are already well developed, Mecket’s cartilage being absorbed 
or used up in the lower jaw. The malleus (fig. 6, m/.) is almost completely ossified ; 
the processus gracilis is still one-third larger than the manubrium (mb.), which is 
short and straight, and nearly parallel with the processus gracilis. The head of the 
malleus is bulbous and large, the posterior angular process (ag.p.) forms a small 
cartilaginous elbow to the manubrium, The hind margin of the bone is oblique and 
sinuous ; altogether this malleus is very much unlike what is seen in the Mascarene 
types. The incus (7.) is quite typical, and has, for an Insectivore, a very large 
processus brevis (s.¢.7.). The stapes (s¢.) is nearly typical ; it is higher, however (or 
longer), and has a smaller fenestra than that of the typical Insectivora ; it is fairly an 
intermediate form between the typical and the Marsupial stapes. Its neck and base 
are not yet ossified completely ; I see no interhyal on the tendon of the stapedius 
muscle. 
The slender epihyal (fig. 3, e.iy.) cartilage is continuous both with the auditory capsule 
above, and with the upper ceratohyal (c.hy.) below ; that tract is now a slender bony 
rod, separated by a cartilaginous piece half its length from the lower ceratohyal (c.hy’.), 
which is straighter, shorter, and stouter. The bypohyal segment is solid, conical, 
short, and articulates by its base with the basal bar ; it is, at present, unossified. 
The thick basal hyoid is U-shaped, and has a bony centre on both the base, proper 
(b.h.br.), and in the thyrohyals (¢.hy.). 
The emargination of the fore edge of the basihyal, and the general breadth of the 
whole of the hinder tract, makes this part, also, intermediate between the hyoid of a 
typical Insectivore and that of a Marsupial. 
On the skull of the Colugo (Galeopithecus). 
My materials for this type are as follows :— 
Stage 1 (a).—A naked, but apparently ripe, embryo of Galeopithecus volans (locality), 
53 inches long from snout to root of tail, with the umbilicus thick and soft. 
Stage 2 (B).— A young specimen of Galeopithecus philippensis, 8 inches long to root 
of tail (well covered with hair). 
Stage 3 (c).—A second young form of the same kind, one-fifth larger. 
Stage 4 (p).—Two adult specimens of G. philippensis, which were taken with the two 
young individuals, in the Philippines, by Professor Mosexry, F.R.S., during the 
MDCCCLXXXV. 2K 
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