54 
MR. W. K. PARKER OK THE STRUCTURE AND 
I have already shown the characters of two kinds from this “region” (R. palustris 
and R. halecma), but they were young ; yet some unexpected and very important 
points were elicited, and will be referred to in the description of this large and most 
characteristic kind. In this species we see those peculiarities of the Batrachian skull 
which set it by itself, making it to differ from other kinds of skulls, carried to an 
extreme degree of development. 
These things bespeak a highly specialised type, and indeed this American Bull-frog 
is a Frog of the Frogs ; his shape, dress, voice, and carriage, all combine to make him 
the representative of his group or “ Order.” 
On the other hand, like all giants, there is much in him that bespeaks an 
ancientness (as if he only remained of the remnant of the giants), and was somewhat 
out of place among the more proud and elegant dwellers in the marshes and miry 
places of this, the newest, epoch. 
In outline this skull (Plate 8) is half an ellipse and very regular ; its greatest 
breadth is, as to its axial length, as 7h to 5f. If the length were measured up to 
a line passing from one quadrate condyle to the other, then the skull would be one-tenth 
longer than when measured up to the convexity of the occipital condyles. In my 
specimen the former reach one-fifth of an inch further back than the latter. 
In R, tigrina (Plate 6, figs. 1 , 2) this distance is only one-sixth of an inch ; relatively , 
however, the distance is the same, for the Indian skull was smaller; in R. hexadactyla 
(Plate 7, figs. 1, 2) the distance is only half as much ( one line). 
This extreme extension of the gape backwards, during metamorphosis, is in remarkable 
contrast with what I find in my oldest specimen of the adult of a small toothless 
Australian Batrachian, viz.: Pseudophryne Bibronii. In this kind, in which the female 
is one inch long, and the male three-quarters of an inch, I find that the quadrate condyle 
reaches very little more than half the relative distance attained to in R. pipiens and 
R. tigrina, or only two-thirds as far back as the occipito-atlantal hinge, measuring from 
the front of the snout, backwards. In that kind the whole suspensorium is arrested in 
its backward movement, when it forms a right angle with the axis of the skull: this 
is very similar to what is seen in the skulls of “ Caducibranchiate Urodeles,” whose 
gape is so much less than in the “ Anura.”* 
The next thing that strikes the eye, after the great extent of the gape, is the very 
small size of the cranial “ barge ” as compared with the huge facial outworks ; its 
average width is a quarter of an inch, scarcely more than that of the Common Toad, 
with a bead little more than half the length of this Bull-frog. 
The occipital condyles are large, near together; more shown below than above, and 
with a gentle emargination between them. The whole occipito-auditory region, right 
and left, is marked by great hills and hollows, and jutting snags, very unlike what is 
* It is a general rule in this “ Order ” that the gape is relatively, as well as really, larger, the larger the 
species "becomes; and in very dwarfed kinds the contracted gape is a correlate of several other arrests 
in the development of the parts of the skull. 
