DEVELOPMENT OF THE SKULL IN THE MAMMALIA. 217 
angle, the hinder edge is then notched twice, and then comes the solid bulbous “ pos- 
terior angular process” (p.ag.) of this highly modified “ articulare.” The main part of 
the malleus has ribbed edges, is limbate, and the neck is flat and thin; on the inside 
the root of the manubrium is thick and rough. 
The incus (7.) shows signs of degradation, being fused with the malleus and 
reminding the observer of the arrested and, in the adult, fixed state of that segment 
of Echidna. The short crus (s.c.7.) is a mere snag; the long crus is very long, feeble 
and bent forwards ; the neck of the orbicular condyle is well bent, very thin, and 
carries a well-made circular facet for the stapes. That bone (fig. 8, sf.) is a miniature 
model of a stirrup, thoroughly normal, and unusually perfect in form. The hyoid 
arch, proper (Plate 31, fig. 9), has become much stronger, and yet more slender, than 
in the young stage (fig. 12). The cartilaginous continuation of the epibyal, from its 
bony stump (fig. 5, ehy.) to the top of the upper ceratohyal (fig. 9, c.hy.), Is a 
complete band of cartilage; the next tract is slender and curved, and is unossified 
in its lower third; the lower ceratohyal (c.hy’.), the hypo- basi- and thyrohyals are 
largely ossified ; the latter (t.4y.) are much longer now, and are bent outwards in the 
middle. 
The interior of the skull was not figured; nor any of the figures made from an 
old specimen. The cribriform plate is very large, oblique, and richly perforated ; 
the median ethmoid, between its halves, is thin, but strong; all the parts, inside the 
front of the cranial cavity, are well ankylosed together. The orbitosphenoids have 
very narrow edges to the hind margin of the cribriform plate ; the basisphenoid has a 
very slight sellar depression. In old skulls the parietals coalesce with the frontals 
and with the fore half of the upper part of the squamosals; so that the sutures left 
are the hinder main part of the sagittal, that between the parietal and interparietal, 
and the hind part of the squamous suture. 
Yet these remains of sutures, the independence of the extensive auditory cap- 
sules, and the general thinness and elasticity of the larger bony tracts defending 
the brain, all help to make this small skull more or less flexible under accidental 
pressure. 
I have not added certain figures made from the skull of the adult Water Shrew 
(Crossopus fodiens); it merely differs from that of the Common Shrew (Sorex vul- 
garis) by its larger size, greater robustness, and a somewhat more intense ossification 
generally. The orbitosphenoids are wider, and the “ foramen ovale ” is quite visible on 
the lower aspect of the skull; in the common kind (Plate 31, fig. 2) the bristle (V*.) 
is seen to pass over the incurved lower glenoid process ; there is a notch between it 
and the hind corner of the alisphenoid (a/.s.), and then a bridge of bone between this 
notch and the fore-end of the great infero-lateral fontanelle. In Crossopus fodiens 
the emerging nerve is bounded in front by a tract of bone, where the notch is in the 
lesser third ; here it appears to pass through the neck of the lower glenoid process ; as 
a matter of fact, the foramen is made by the confluence of the alisphenoid with that 
part of the squamosal. 
MDCCCLXXXV. oF 
