178 
MR. W. K. PARKER ON THE STRUCTURE AND 
6. The ethmoidal roof gives off large superorbital outgrowths. 
7. The palatine bones are unusually developed, taking on the dilated form of the 
corresponding cartilages. 
8. The pterygoid bone, like the cartilage on to which it is grafted, is slender, but it 
articulates, by suture, with the bony skull, and fixes the pedicle. 
9. There are neither inter- nor supra-stapedial. 
10. The basal plate is largely membranous in front, and all the “lobes” are small. 
11. There are no septo-maxillaries. 
12. The fronto-parietals are narrow, arrested bands. 
49. Hyla rubra. —Adult male; 1 inch 11 lines long. South America. 
This is a lightly built, but strong, skull (Plate 33, figs. 6, 7); its greatest breadth is 
to its length as 11 to 10, and its general outline is seven-twelfths of a very neat oval; 
the incurving of the quad rat o-jugal (q-j-) gives a sixth of the (supposed) other half of 
the figure. The condyles of the quadrate (q.c.) reach as far back as the upper edge of 
the foramen magnum ( f.m .). 
It is a flat, wide skull, the “parotics’' - beyond the horizontal canal (h.s.c.) doubling 
the width of the capsule, right and left. The axial extent of the hind skull is only 
two-thirds as great as that of the other two regions, which are equal. 
Measured across the etlnno-palatine wings within the maxillaries ( e.pa ., mx.), in 
front, and across the tegrnen tympani of each side within the squamosals (sq.), behind, 
the chondrocranium has the same breadth. A considerable synchondrosis exists above 
and below, at the mid-line ( f.m .); between the small, oval, posterior condyles ( oc.c.) 
the basal outline is convex, and is equal to both the facets in breadth ; the arch, above, 
comes short of the basal plate only moderately; the obliquity of the foramen magnum 
is not great. 
The extent of the outstanding ear-capsules is twice as great against the skull as at 
the tegmina (inside sq.) ; each tegrnen is ossified for one-third of its extent, and the 
bony tracts are not divided into a prootic and an ex-occipital (jpr.o., e.o.) ; the foramen 
ovale (V.) is not quite enclosed by this bony tract. Below (fig. 7), the bone only leaves 
a scooped cartilaginous space, margined by a bony balk, for the pedicle (pd.) and a 
small tract running from the setting on of the stylo-hyal (st.h.) to the fenestra ovalis 
(st.). The hinder third of the interorbital space is cartilaginous, and the large optic 
fenestra (II.) occupies its middle. That region is almost oblong—it dilates a little 
at both ends; it is only three-fifths the width of the sub-oval orbital spaces. The 
single fenestra is long-heart-shaped ; the fore end of it has been filled in by periosteal 
growths from the girdle-bone; the lateral tegminal growths are wide. This is a very 
rare ethmoid; its superorbital region is unossified, and grows out and back into a narrow 
cartilage with a sinuous outline ; this process carries a distinct oval superorbital (s.ob 1 .) 
which is turned forwards. This free cartilage occurs again in Phyllomedusa and Alytes 
