274 
MR. W. K. PARKER ON THE STRUCTURE AND 
which for a time holds the stapes in its place ; it is, however, absorbed afterwards, but 
remains in the related genus Myogale. In nearly half-grown young Moles the malleus 
is quite like that of the Marsupials, and it is an evident articulare, with copious wild 
growths of bone, sub-distinct and answering to the “ angulare ” and “ supra-angulare ” 
of a Reptile or Bird. This malleus in its articular part has two endosteal and one 
ectosteal bony centres. Meckel’s cartilage, long continuous with the malleus, is 
nearly as massive as in the Hedgehog, and has a more distinct separate ossification in 
its subdistal part—a long independent, but temporary hypobranchial bone. 
The Mole shows a most remarkable development of the endocranium, which, twenty 
years ago, suggested to me that its skull retained unmistakable Monotrematous 
characters. In the large young of the Echidna and Ornithorhynchus the solidity of 
the chondrocranium is immense—like that of a C'himceroid Selachian—and the investing 
bones are thin and splintery. I have not made out the mode of ossification of the 
inner skull in those types, but in spirit, if not in the letter the Mole agrees with them, 
that is in the great development and independence of the inner skull. The “opisthotic” 
bones ossify the normal petromastoid region, whilst the “ prootic ” bony centre 
begins in its right place on the front edge of the cartilaginous capsule and then runs 
away from it into the wall of the skull; thus there is a large bony tract in the 
temporal region, between the small squamosal and the large interparietal, which is not 
one of the ordinary outer cranial bones, but an enclocranial bony tract, overshadowing 
and yet imitating the true temporal bone or squamosal. This bone is represented by 
three separate centres in Osseous Fishes, namely, the prootic, pterotic, and sphenotic, 
whilst their true auditory region is ossified by the epiotic and opisthotic ; the epiotic 
is only subdistinct in the Mole. 
If I am asked wdry I dive so far down for my illustrations instead of being satisfied 
with wdiat Reptiles and Birds would show me, my answer is that those are often of 
no use for comparison, for they are as thoroughly specialized for their own mode of life 
as the Mammalia, generally, and are as completely, and often more completely, trans¬ 
formed from the original archaic type or types. 
Thus the Mole, like most of the Edentata lately described by me, suggests as the 
root-stock of the Eutheria, generally, not Marsupials (Metatheria) as we know them, 
but Prototherian forms, in which, in ages long past, the existing Monotremes and 
Marsupials had a common origin. 
The Shrew ( Sorex vulgaris ) represents another family of the Insectivores, the 
Soricidm. It combines the characters of the Mole and Hedgehog with peculiarities 
of its own that are manifestly due to dwarfing ; many things are suppressed, as if 
there was not room in so small a skull for their development. The pituitary hole 
re-appears, and the pterygoid cartilage—but the tympanic wing of the alisphenoid 
and of the basisphenoid are gone; the malleus does not show itself so unmistakably 
Marsupial, and Meckel’s cartilage is slenderer. The sheathing alisphenoids are w r ell 
seen ; the squamosal is small, low down, and devoid of a jugal process ; the jugal bone 
is suppressed. 
