92 
MR. W. K. PARKER OK THE STRUCTURE AND 
manifestly seen to be an external crest of the trabecula, a continuation of the cranial 
wall, but in front of the cranial cavity. 
For the rest, the quadrate region and its condyle (</.), the mandibles (fig. 7, mk) and 
the lower labials (LI.) have merely increased in size since the last stage. The same may 
be said of the fronto-parietals (f.p .); they are a little straighter, however. But the 
parasphenoid (fig. 6, pa.s.) has been transformed into the normal shape, or nearly; the 
notch is now relatively much smaller : its shaft is long and wide also ; the basi-temporal 
wings are now developed, they are pointed, raggedly lobate, and meet in a triangular 
“ handle.” 
19 (continued).—(C) Cystignathus ocellatus var.—Adult male; 5^ inches long. Dominica. 
This large sub-typical Frog has a skull (Plate 16, figs. 1-5), whose length is to its 
breadth as 7 to 8^; it is a very regular half-oval in outline, and the condyles for the 
lower jaw reach, very nearly, as far back as those for the atlas. Being of great 
breadth, the auditory regions are extended like outspread arms, the parotic processes 
being as wide as the capsules proper, outside the horizontal canals. 
The extent of the ossification of the endocranium is normally Ranine, and there 
is clear tract of cartilage above and below the foramen magnum ( fm .), and the 
ex-occipitals and prootics (e.o., pr.o.) are distinct. 
The occipital condyles ( oc.c .) are large, reniform, postero-inferior, and separated by a 
space less than their own size; the occipital arch itself is of great width, and well 
marked off from the auditory capsule, especially above. This is due to the great 
size of the epiotic eminence (ep.), caused by the arch of the posterior canal; this 
eminence is unossified. So also is the outer half, below, and the outer third, above, 
the prootic not reaching, even there, as far as to the squamosal ( sq .). Thus the whole 
of the extensive tegmen tympani ( t.ty .) is unossified. 
Besides the high epiotic region another ichtliyic character appears (seen to a less 
degree in Rana pipiens, Plate 8), viz. : an extensive “ pterotic ” crest (pt.o.); this is a 
backward and outward sigmoid process of the tegmen tympani, which doubles the 
extent of the margin and overhangs the large annulus tympanicus (fig. 3, a.ty.), behind. 
The prootics (pr.o.) reach as far as to the middle of the space between the 5th and 2nd 
nerves (V., II.); the latter lie in a fenestra which reaches half-way from the prootic to 
the girdle-bone (eth.). The interorbital region widens steadily from behind forward, it 
is rather hollow above and below, for the side view (fig. 3) shows a concave outline 
both to the roof-bones and the parasphenoid (fp., pct.s.). 
This enlargement forward is due rather to the growth of an “ eave over the fore part 
of the orbit than to any great increase in the size of the cranial trough within ; but for 
that superorbital expansion the cranial trough would be seen as somewhat spindle- 
shaped, bellying in the middle and narrower at either end. The outer edge of the 
superorbital expansion is unossified, and in its fore edge the orbito-nasal nerve (fig. 3) 
