194 MR. W. K. PARKER ON THE STRUCTURE AND 
On the outer face (fig. 10) that process is well marked off, as if it had formed 
separately, and then became anchylosed to the straight process; here, also, the upper 
lobe has a very distinct form and outline, behind, whilst the lower lanceolate tract is 
less distinct. 
On this face we miss the pneumatic recess, but get a view of the remnant of the 
cartilage that separates the epiphysis in the manubrium (fig. 7, mb.) from the main 
part of the bone. It is evident that, about the time of weaning the young Mole is 
developing, in a rough, irregular, and abortive manner, the well-known “ 
angulare ” 
and “supra-angulare” of the Oviparous tribes, in addition to the “articulare externum,” 
and the two endosteal articular tracts that are found in Holostean Ganoid Fishes. 
We shall soon see what becomes of all this eftort to restore the old compound 
mandible. 
The Ayoid arch (Plate 28, fig. 8), when detached from its two upper elements (the 
epihyal and stapes), shows a considerable advance upon the last stage (fig. 7), all the 
bony shafts are rapidly developing along the cartilaginous rods; the articulations, 
also, are very distinct. 
Tweljth Stage.—Young Mole; three-fourths grown. 
Among my materials—gathered during the last forty years or more—I found the 
malleus of a somewhat older Mole than the last ; it is of great importance, for it shows 
(Plate 25, fig. 4, inner wew, fig. 5, outer view) the softening down, by absorption, of 
much that was rugged and irregular in the last stage. The processus gracilis is still 
very large, and is cochleate proximally; the crest and the pretympanic sickle are 
gone. But the cartilage separating the manubrial centre (mb.) from the main bone, 
on the outer side, is still evident. Of the same age also are the other ossicles here 
figured, the incus (Plate 25, figs. 6, 7) and the stapes (Plate 28, fig. 11), and also the 
annulus (Plate 25, fig. 11). 
Both the orbicular facet for the stapes (/.¢.2.) and the short crus of the incus (s.¢.2.) 
are feebly developed and look towards the Monotrematous condition ; the whole inner 
face is open to the tympanic cavity. 
The stapes (Plate 28, fig. 11) cannot be detached in this stage, as in the adults of 
some other Insectivores, e.g., Myogale moschata and M. pyrenaica (see DoRAN, op. cit., 
p. 435). 
This is a very remarkable modification (Plate 28, fig. 11, st.), and its transitoriness 
in this type is also noteworthy; the Mole gets beyond Myogale in this respect. This 
little bone is kept in its place by the ossification of the outer sheath of the stapedial 
artery (st.a.); a sheath similar to that which protects the outer part of the internal 
carotid in the Bird. There, the bony arterial sheath traverses the light diploé ofthe basis 
cranii between the basitemporal plate and the proper spheno-occipital skull floor. Iam 
under the impression that this sheath is formed just as the stapedial artery becomes 
