158 
MR. W. K. PARKER ON THE STRUCTURE AND 
10. The unique ossification of the large basal plate, and the crested growths of the 
thyro-hyals. 
In the next kind of dwarf “ Polypedatid,”—a smaller species than the last and from 
another region,—the signs of arrest are more numerous, and some of these stoppages 
must have taken place early in the larval stage; moreover there is but little sign of 
compensating growth, in over-ossification and the like, such as is seen in the one just 
described. 
42. Rappia (Hyperolius) hi color. —Adult female; f inch long. Dog-trap Road, 
Param atta, A ustralia. 
This is a rather long skull, for the length and greatest breadth are equal. The 
quadrate condyles (Plate 19, figs. 6, 7, q.c.) end opposite the middle of the medio- 
stapedial (rn.st.). The mid skull is one-third longer than the other two regions, which 
are equal to each other in this respect; they are both moderately broad, but the mid 
skull is very broad. 
The interauditory region is nearly as wide as the interorbital, and this latter 
increases in width forwards. The “ tegmen craniiis very slight in front, largely 
covers the hind brain, and there is left a fontanelle ( fo .) which is evenly egg-shaped, 
and has its wide end in front. 
There is a very narrow band of cartilage bounding the fontanelle on each side, but 
this is not continued downwards into the wall, which is membranous, except for a short 
distance at each end. 
There are two rather large secondary fontanelles in the extensive interauditory roof. 
The occipital condyles ( oc.c .) are small, sub-reniform, and postero-inferior; they are 
separated by a straight basal tract equal to both in width. The basal cartilage is equal 
to one condyle in width, and the upper or supraoccipital cartilage is as wide as the 
intercondyloid space. 
The four bones ( pr.o ., e.o.) are larger than in the last; the ex-occipitals reach the 
fenestra ovalis below, and are wider above ; the prootics cover the anterior canal (a.s.c.), 
nearly, floor its “ampulla” below, and go round, but not in front of, the foramen 
ovale (V.). There is a moderate tegmen tympani (fig. 6), and the canals and vestibule 
bulge out above and below (A.s.c., a.s.c., p.s.c., vb.). 
The tegmen cranii becomes a narrow band directly it passes into the interorbital 
region, for the trabeculae (tr.) have not enlarged, relatively, since the legs of the 
Tadpole began to bud out, only the intertrabecular tract of cartilage was added. 
The optic foramen (II.) is large, but the optic fenestra (or fontanelle, ofo.), which 
is large in several types of small Australian Anura, here occupies nearly all the orbital 
region; it is one-tliird the length of the skull. The bulging floor of the skull widens 
towards the ethmoidal region, and then, behind the true nasal region, there is a com¬ 
plete girdle for a short distance—not a complete bony girdle, however, yet there are 
