DEVELOPMENT OF THE SKULL IN THE BATRACHIA. 
127 
than the main bar, and end by a ragged oblique edge, which runs to a point in front, 
reaching nearly to the Eustachian opening ( eu.). 
The middle of this hind part is raised into a lozenge-shaped convexity, but the main 
bar, which is three-fifths the width of the trough of the cranium, is itself a deep 
trough. 
Between the foramina ovalia (V.) it is compressed a little, is widest between the optic 
nerves (II), and then scarcely lessens to its rounded ragged fore end, where it reaches 
the thick bosses of the vomer (v.) that carry the teeth. 
Those bones (fig. 2, v.) are very thick in their dentigerous portion, where they form a 
lobe that runs outwards and a little forwards ; the thinner part forms a strong spike in 
front of the internal nostrils ( i.n .), and a broad diverging lobe in front of the spike, 
which reaches the maxillary under the angle of the “ subnasal lamina ” ( s.n.l. ). 
This cranial building is thus finished below and above ; its roof, floor, side-walls, 
partitions, chambers, and outworks are all essentially such as we see, on a small scale, 
in the Common Frog. But the great size of this skull, and the extension under the 
skin of thick dense bone, ornate with a honeycomb pattern of hollows and papulate 
ridges passing into pearly grains, makes it in appearance very unlike its simple 
“norma.” These modifications may be classed under one head as modification No. 1. 
2. The upper fontanelle appears to be single. 
3. The long inner process of the pterygoid aborts the joint of the pedicle. 
4. There are distinct superorbital ledges. 
5. The quadrate is largely ossified by the quadrato-jugal. 
6. There is no inter-stapedial segment. 
7. The extra-stapedial is suborbicular, and its supra-stapedial process is confluent 
above. 
8. The stylo-hyal is confluent above. 
9. The basal plate is very short, the hypo-hyals have no lobe, and the hind lobe is 
very large and emarginate. 
These are the few, and for the most part gentle, differences between this skull and 
that of the norma, 
30 (continued).—(B) C. Gayi. —Larva; 4f inches long ; tail, 2f inches ; hind legs, 
■g- inch. Chili. 
In the large Tadpole of this species the chondrocranium (Plate 22, figs. 2-5) is 
seen to differ in many points from that of the larvse of the American Bull-frogs 
(Plates 3 and 4), and of Pseudis. 
It may be compared with the same (my first) stage in Rctna pipiens (Plate 3, 
figs. 1-3), Ranct clcimata (Plate 2, figs. 5-7), Pseudis paradoxa (Plate 2, figs. 1-4), and 
with a somewhat more advanced stage of Cyclorhamphus culeus (Plate 22, figs. 6-9), 
and with the larval skulls of Cystignathus, Phyla , Bufo, &c., in other Plates. 
Its true relationship will be at once seen by a comparison of the figures on this 
