104 
MR. W. K. PARKER ON THE STRUCTURE AND 
space, and contains the rudiment of a basioccipital bo,ne (fig. 2) as a frail bony “ cephalo- 
style.” 
The upper tract is of the same width at the foramen magnum, but widens out, 
wedge-like, to the fontanelle ; it contains the rudiment of a supraoccipital bone as a 
slight endosteal deposit. 
The antorbital ( axillary ) tracts of the ethmoid are ossified ( etli .), not, however, as 
a " girdle-bone,” but as in “Urodeles” as a pair of “ sphenethmoids;” these occupy 
about three-fifths of the ethmoidal cincture—perfect here for a short distance. Below 
(fig. 2), the two bones are separated by a distance less than their own width ; above 
(fig. 1), they come a little closer together, ending there as sigmoid “ horns,” turned 
forwards till they nearly touch the conchoidal nasal roof. 
These bones, laterally, just run round the end of the long oval interorbital fenestra; 
in their interspace below there is between these two ecto-ethmoids an evident, endosteal, 
“ mesethmoidal ” tract like the azygous endosteal patches in the hind skull. 
Here, once more, we come athwart the familiar “ perpendicular ethmoid,” and the 
basi- and supraoccipital bones. 
The palato-suspensorial arches have thin bony plates (pa., pg.), and these, as well 
as the bones that surround the face, are normal, if compared with a young Common 
Frog of the first summer. 
The vomers (fig. 2, v.) are small and toothless; the parasphenoid ( pa.s .) is narrow, 
especially in the fore part, yet it is, essentially, typical. But the fronto-parietals 
(fig. 1,/p.) are by far the slightest and most delicate I have yet seen : they reach to 
the conchoidal nasal roof in front, and partly cover the anterior canal ( a.s.c .) where 
these needle-like bones become roughly pedate. These bones only cover the outer edge 
of the arrested lateral rudiments of the “ teamen cranii.” 
The nasals and the squamosals (n., sq.) are under-sized but quite normal; so also 
are the parts of the mandible (fig. 3), and the hyo-branchial plate with its processes 
(fig. 4). 
The annulus (fig. 1, a.ty .) is open above and rather small. The stylo-hyal ( st.h .) is 
articulated, above; the Eustachian passage (eu.) is of medium size and reniform, with 
the concavity looking outwards and backwards. 
The stapes (fig. 5, st.) is between a lozenge and an oval in shape; it is large, and 
has a short stalk. 
The cartilaginous enlargement on the oblique end of the columella is not segmented 
off as a distinct inter-stapedial. The medio-stapedial (m.st.) lessens rapidly from this 
cartilaginous process, and ends as bone, a little behind an oval, decurved, thick but 
small, foot of cartilage—the extra-stapedial ( e.st .) ; there is no ascending process from 
this lobe. The labial cartilages ( u.V-.u.l 2 .) are normal. Many of the things that dis¬ 
tinguish this from the typical skull depend upon arrest, and are such as can be seen in 
a young Common Frog, five or six months old. 
