172 PROF. W. K. PARKER ON THE STRUCTURE AND 
The Skull of Sieboldia maxima mas adultus, 4 feet 2 inches long. 
The general form of this skull (Pls. XXXVI. & XXXVII.) is semielliptical and 
very flat; the greatest breadth is across the quadrate condyles; and this measurement 
is about one tenth greater than the length along the axis. The maxillary arch reaches 
outwards so far as to give a measurement just intermediate between the length and 
the greatest breadth ; its backward stretch is only halfway from the fore margin to the 
condyle of the corresponding quadrate. 
The direction of those condyles is outwards, a little downwards, and slightly back- 
wards; behind they reach as far as to be opposite the narrowed waist of the occipital 
cincture. 
Generally speaking, the skull is subconvex above, and gently hollow below; but 
there is, notwithstanding the persistence of the frontal and sagittal sutures, a definite, 
rather sharp, median crest. 
The whole maxillo-premaxillary arc is ankylosed into a single bone; the palatines 
and vomers of the same side are confluent; and the parasphenoid has coalesced with 
the occipital bones below: this is due to the great age of this individual. The pub- 
lished figures do not show this'. 
On the whole, the metamorphism of this skull has been arrested at the same stage 
as that of an ordinary “ Caducibranch” of the first summer, or immediately after the 
loss of the gills. See Plate XL. figs. 6 & 7. 
A. The Investing Bones of Sieboldia. 
The superficial bones are dense, smooth, and often perforated by vessels; they have 
a considerable thickness in several instances; and they form about half the materials of 
the building. But there is no definite line to be drawn between those investing bones 
that keep entirely free from the chondrocranial tracts and those that graft themselves 
upon certain parts of those tracts: for instance, the palatine keeps free from the 
cartilage; but its segmented pterygoid process (the “‘ pterygoid” of the adult) ossifies 
all the proximal part of the pterygoid outgrowth of the suspensorium. 
The three pairs of submesial roof-bones (parietals, frontals, and nasals) reach from 
the foramen magnum to the outer nostrils (Pl. XXXVI. fig. 1, p, f, n, e. n), and form 
an oblong tract which only partially hides the underlying structures; for the endo- 
cranium is spread out below, and contracted at the top of the low side walls. These 
symmetrical upper plates are all imbricated from before backwards ; and the parietals (p) 
have only their square hinder part, or about two fifths of their length, free from the 
overlapping frontals (f'). The fore part of each becomes a long, sharp, slightly out- 
turned wedge of bone. 
* © Fauna Japonica,’ pl. viil. figs. 1, 2; Wiedersheim (6), pl. ii. figs. 21, 22. 
* One of the lesser Japanese Urodeles, viz. Onychodactylus, undergoes less metamorphism than this gigantic 
kind (see Trans. Linn. Soc., Zool. 1880, pl. xix. figs. 1-8). 
