40 
MR. W. K. PARKER ON THE STRUCTURE AND 
Skulls of adult individuals of the genus Rana. 
a. European species. 
6 . Rana temporaria. 
I have just referred to the characters of this (typical) species, described and figured 
in my first paper (Phil. Trans., 1871, Plates 3-10, pp. 137-211). I shall use it as 
a norma, after eliminating its one aberrant character, viz.: its sub-distinct “ meta- 
pterygoid.”'"' 
7. Rana esculenta. 
For a description of the skull of this species the reader is referred to Professor 
Huxley’s article on the “Amphibia” (Encyc. Brit., vol. ix., pp. 750—771).+ 
h. Oriental species. 
8. Rana gracilis. —Adult male ; 1-y inch long. Ceylon. 
The skull in this small species (Plate 6, figs. 6-10) differs but little from that of the 
Common Frog (op. cit., Plate 9); its endocranium is more ossified, but its mandibular 
hinge does not reach so far back : the general form is very similar, being half a rather 
long ellipse. Between the oval occipital condyles there is a large right-angled space 
(figs. 6, 7), and the outline of the foramen magnum (fan.) above is a large crescentic 
emargination. 
The superoccipital soft tract is twice as wide as the basioccipital, but they are both 
of small extent. The whole occipito-otic mass is a large transversely-placed oval, the 
ends of which are nearly ossified above, but with a large tract of cartilage below, which 
runs across from side to side between the prootics and ex-occipitals ( pr.o ., e.o.). The 
passages for the main nerves (II., V., IX., X.) are large and very clearly seen in the 
lower view (fig. 7). The optic nerve passes through a large membranous fenestra, 
which has a narrow tract soft behind it, and a broad tract in front; half the inter- 
orbital region is unossified, but the foramen ovale (V.) lies in the centre of the large 
postorbital face of the prootic. 
Above, from beyond the horizontal canal to the edge of the tegmen tympani, there 
is a soft tract; but from thence inwards to the lesser fontanelles all is bony, and 
the prootics and ex-occipitals are quite blended, walling in the canals and covering 
most of the hind archway of the skull. The fore half of the interorbital region is 
occupied by the common “ sphenethmoid,” or girdle-bone (eth.), which does not take 
Up all the ethmoidal region; it projects in front above, but is emarginate below. The 
fore part of the ethmoid, all the nasal region, and the transverse ethmo-palatine bars 
* In my figures of the nasal region of this species (“ Batrachia,” Part 2, Plate 54, figs. 1, 2) tlie 2nd 
tipper labial is figured too bigb up, and the pro-rhinals are lettered c.tr. 
f This species has the pro-rhinals distinct, as Professor Huxley’s figure (p. 755, fig. 9) correctly shows. 
This distinctness is seen again in Dactylethra (Phil. Trans., 1876, Plate 59, fig. 6, u.l c .) ; it is there 
lettered u.l c . hy mistake. 
