208 MR. W. K. PARKER ON THE STRUCTURE AND 
this abortively developed orbitosphenoid. The sphenoidal fissure is a long space 
under the orbitosphenoidal bar, and over the alisphenoid; through it, not only the 
orbital, but the optic, nerves also pass. The hinder half of the alisphenoid (al.s.) 
only can be seen in this view; the bone is twisted over the notch for the 3rd 
branch of the trigeminal (V*.). The notches and shoulder of the basisphenoid (b.s.) 
are well seen; there is scarcely any sellar concavity on its upper face. Much 
cartilage is still seen m the synchondrosis between the two basal bones and between 
the elements of the occipital arch; and also, above, where the auditory and supra- 
occipital regions unite. The cartilage in the auditory recesses (see Plate 31, fig. 11, 
.8.C., p.s.c.) are scarcely visible in this aspect, but the capsule appears to be almost 
wholly ossitied; the base of the floccular recess, the holes for the portio moliis 
(VIIL.), and the bridge under which the portio dura (VII.) runs, are well seen. 
In front of the very shallow imeatus internus the capsule sends forwards a bony snag, 
which helps the toothed rim of the cochlear region to give some bony support to 
the largely membranous region in front of it. 
Third Stage (continued).—Dissections of the visceral arches of the young Shrew. 
I have not figured the fore half of Meckxrt’s cartilage, which still persists, not 
larger, but not evidently lessened, inside the lower jaw (see Plate 29, fig. 2). Towards 
the malleus (Plate 29, fig. 6, ms.) it is seen as a solid terete rod, having a bony style 
supporting it further forwards than the manubrium (mb.) extends. But that primary 
style of bone has grafted itself upon, and set up extensive ossification in, the head of 
the malleus (i/.). This rambling bony tract has forced its way down to the neck of 
the manubrium, but has left a large core of cartilage in the middle of the head. 
The partly bony head of the malleus is quite normal, and has the tensor tympani 
(¢.t.m.) attached to its inner face ; but the manubrium and the posterior angle of the 
part from which it springs are very remarkable. The slender manubrium looks like 
the tube of a retort, the bulb of which is imitated by the angle; the main part of 
the head projects well, backwards, below the articular facet ; the bony matter then 
forms a ring round a contracted tract, or waist ; from this part the bulbous tract hangs, 
so to speak. Thus the bulbous head, the enlarged body, and the subglobular 
“anole” form three enlargements, all in one line, and that at a right angle to 
Meckew’s cartilage, and to the manubrium. The incus (¢.) is rather small, and its 
articulation with the malleus is becoming indistinct ; the short crus (s.c.7.) 1s very 
short ; the long crus (/.c.7.) is rather longer than ordinary ; the head is unossified, and 
so also is the inturned orbicular facet. 
The stapes (st.) is large, relatively, and has a perfectly stapedial shape ; it is nearly 
all bony, the top and base being still soft; I could not find any separated interhyal 
in the tendon of the stapedius muscle (s#.7.). 
The short crus of the incus fits into a little cup close above the part where the 
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