DEVELOPMENT OP THE SKULL IN THE MAMMALIA. 
29 
canal (p.s.c.) shining through ; below and behind it the occipital condyle ( oc.c .) ; and 
above that the occipital arch and one of the supra occipital bones (s.o.). 
In this view the peculiar forward position of the nasals ( n .) ; the small inferodateral 
premaxillary ( px .); the large maxillary (mx.), with its long nasal suture, its deficient 
upper facial plate, and its notched jugal process, are seen. The infraorbital foramen 
(V 2 .) is very low down ; at a moderate distance above it is the large, shell-like 
lacrymal (L), with an antorbital and a facial region, and the canal (he.) between, 
Here, as well as in the upper view, we see what a large amount of space is covered 
by the frontals (/.). The preorbital part of each bone is swelling, to fit over the huge, 
complex nasal capsule, and then, behind the supraorbital “ waist,” the bone swells 
again to cover the hemispheres. The orbital plate is also very large, and hides most 
of the large orbitosphenoidal plate; the optic nerve (II.) can just be seen emerging 
from its stem. The parietals (p.) are roundish shells, like the halves of a “ bivalve ; ” 
they nearly reach the frontals in front, and rest upon the squamosals ( sq .) below. 
These latter bones are nearly as large as the parietals, but of a very different shape. 
They reach nearly as far back, and much further forwards, but are not so deep. A 
large triradiate space separates the three main bones, here, below which the temporal 
fossa passes directly into the wide, gaping orbit. The zygomatic process of the 
squamosal is strong, and is clamped by the straight, tlnckish jugal (J .), behind which 
we see the edge of the glenoid cavity. The postglenoid process is hollow, and of a 
triangular form ; the posttemporal process is rounded. 
The lower jaw is very elegant, with its arcuate general ramus (d.) and its slender 
coronoid process separated by a narrow notch from the articular condyle, and the 
latter by a smaller notch from the angular process ( ag.p .); much solid cartilage still 
remains in these parts. 
The endoskeletal part of this arch (Plate 2, fig, 8 ; and Plate 5, fig. 4) is of great 
interest. Meckel’s cartilage ( mk .) is full-sized, a long and solid rod, passing inwards 
and forwards to melt into its fellow in front. Behind the massive condyloid cartilage 
(Plate 5, fig. 4, ed.p.) the bony plate of the malleus is seen, under the dilating part of 
this primary jaw. The head of the malleus (ml.) has a very deeply scooped saddle- 
shaped condyloid surface for articulation with the incus (i.) ; below this, the cartilage 
grows in a right angle to the main bar, and then forms the manubrium (m.rnb.) by 
growing forwards again, as a slender terete rod. This is the f! internal angular 
process” of the Ovipara ; but the posterior process ( p.ag .) is also to be seen as a 
tubercle above and behind the elbow of this long process. On the inside, one-third 
the way up, we see the tensor tympani muscle (t.tm.). The incus (i.) has no ectostosis 
at present; its articular surface is a deep, oblique saddle ; its short crus ( s.c.i .) is a 
solid cone, and its long crus ( l.c.i .) is large, long, somewhat constricted proximally, 
and supplied with a large interned discoid facet for articulation with the head of the 
stapes (st.). 
That top piece of the hyoid arch (Plate 5, fig. 4, st.) is a solid little “ stirrup,” with 
