so 
ME. W. K. PARKER ON THE STRUCTURE AND 
I have been able to compare it with the early skull—twice as advanced, and yet 
with a very perfect chondrocranium—in the Armadillo and the Unau, amongst the 
Edentata. 
But in types that have yet to be described, especially the Marsupials and 
Insectivores, I find early crania differing in various ways, but quite normal, and with 
a well-developed chondrocranium. 
In the Monotremes I have the most important, because most radical, types for 
comparison; but in both genera— Ornithorhynchus and Echidna —in young two or 
three times as advanced as this embryo, the chondrocranium is most massive and 
well developed—almost Dipnoan. 
Both in the early skull of the Marsupialia and of the Insectivora I shall be able to 
show how gentle the modification is of a Mammalian skull at this stage, from that of 
the embryo Crocodile. Even if that good, practically fundamental type of skull of a 
well-developed Amniote (see Trans. Zool. Soc., vol. xi., plate 65), be compared with 
those of the Tatou and Unau just described (Plates 2 and 8), it will be evident that we 
have in the chrondrocranium of that Beptile everything we want, in a generalized form, 
out of which to frame (mentally) the much more specialized skull of a normal Mammal. 
But there are other Sauropsida whose skulls have undergone, in various ways, the 
uttermost degree of specialization—I refer to the Ophidia and Carinate Birds. 
In explaining this early skull of the Pangolin and also its latter stages—even that 
of tire adult—I shall have to show a parallelism in several things between the skull of 
this low Eutherian, and of those two extreme forms of the Oviparous Amniotes— 
the Snake and the Flying Bird. 
The earliest skull, worked out by me, of the Ostrich (Phil. Trans., 1866, Plate 7), 
being at the same stage, is very profitable for comparison ; yet, when all is done, and 
the likeness of this skull to any or all of these Sauropsidan types has been shown, 
there will still remain all that is strictly and absolutely Mammalian, the result of a 
transformation of various parts that suggests a true historic metamorphosis which 
once lifted up the Mammal, when just emerging from its low larval form, far above the 
platform of the other Amniota—the Sauropsida,—whether scaly or feathered. 
The lower view of the skull (Plate 11, fig. 1) shows that the nostrils ( e.n .) are large, 
and obliquely inferior in position ; they are roofed over by dilated alinasals ( al.n .), 
which have a wide base (n./). 
All the beginnings of the ectoskeletal tracts are fine bony films, and are very far 
from investing the parts they are intended to cover. 
The premaxillaries (px.) are small, V-shaped bones, with their rounded angle fore¬ 
most ; them proper dentary tract is no larger than their palatine process, which is short 
at present; afterwards (fig. 8) it is long, having received the addition of the small 
corresponding anterior paired vomer (fig. 1, v.). 
Each maxillary ( mx .), as seen from below, is a leafy lanceolate bone, with a 
notched hinder end and an inferior ridge. This ridge is the closed alveolar region ; it 
