54 MR. W. K. PARKER ON THE STRUCTURE AND 



I have already shown tlie characters of two kinds from this "region" {li. paludris 

 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 difier from other kinds of skulls, carried to an 

 extreme degree of development. 



These things bespeak a highly specialised type, and indeed this American Bidl-frog 

 is a Frog of the Frogs ; his sliape, diess, 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 7^ to 5J. 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-Jifth of an inch further back than the latter. 



In R. tigrina (Plate 6, figs. 1 , 2) this distance is only one-sixth of an incli ; 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 i\ie female 

 is one inch long, and the male three-quarters of an inch, I find that the quadrate condyle 

 reaches very little more than hnlf the relative distance attained to in R. j^ipiens 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 witli the axis of the skull : this 

 is very similar to what is seen in the skulls of " Caducibrauchiate Urodeles," whose 

 gape is so nmch 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 tlie huge facial outworks ; its 

 average width is a quarter of an inch, scarcely more than that of the Common Toad, 

 with a head little more than half the length of this Bull-frog. 



The occipital condyles are large, near together ; more showm 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 tliis " Order " tlint tbi^ gape is relativel)-, 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 developuieut of the parts of the skull. 



