166 PROF. G. B. HOWES AND W. RIDEWOOD ON [Mat. 6, 



the head of the outermost metacarpal, especially in Xenophrys, in 

 the adult of which it carries a distinct bony element (5, fig. 16), 

 regarded by us as a 5th carpal (p. 1.54). It is worthy of remark 

 that in its mode of ossification this element conforms in every 

 detail to that observed for the other capalia. 



Born asserts that he found (6, p. 63) in a Pelohates larva a 

 centrale carpi, identical with that figured by him in the young of 

 Alytes ; and he expresses his doubts as to whether the same does or 

 does not regularly fuse with the 5th carpal (our postaxial centrale, k) 

 in the adults of both genera. It must suffice to point out that we 

 have not here observed the presence of that cartilage which he calls 

 the centrale, and the statements already made by us for Alytes 

 (p. 158) apply equally to this genus. 



This preaxial centrale (naviculare, n) may or may not reach the 

 radius in individuals of a species. In the Pelobates figured (fig. 18) 

 it is represented as nearly touching that bone, but in the other 

 carpus it did not extend more than halfway towards it. We have 

 already stated (p. 159) our reasons for regarding this ascending 

 lobe of the naviculare as purely secondary. 



Extremes of modification of the poUex are met with within the 

 limits of this small family. In Pelobates and Xenoplirys it consists, 

 excluding its carpal {po. i.), of a small styliform structure which is 

 quite unsegmented ; in Pelodytes, on the other hand, it is very large 

 and swollen (fig. 1 1, po. i.-iii.) and definitely segmented. In all three 

 genera the rotation of the hand upon the fused radius and ulna is 

 very marked ; and in Pelodytes this reaches its maximum, having 

 gone on through more than a right angle (fig. 11). Comparison 

 with the other two genera suggests that the great development of 

 the pollex may be in some way associated with this distortion ; and 

 we are inclined to ascribe to the same cause a distinct ossification of 

 the distal extremity of the ulna here met with (* of fig. 11) \ 



In Pelodytes the carpus is exceptional among those of this family, 

 owing to the fusion of the postaxial centrale and fourth carpal to 

 form one bone, the capitatura (4. k, fig. 11). 



Hind Foot (figs. 12, 13, 17). 



It is interesting, in the light of the facts concerning the fore foot, 

 to note that the extremes of modification undergone by the astragalus 

 and calcaneus in the Anura are exemplified in this family. In 

 Pelodytes (fig. 12) they are confluent for their whole lengths, much 

 elongated and slender in the middle ; in Pelobates they are relatively 

 shorter than in any Frog which has come under our notice. Xeno- 

 phrys is, in respect to relative length, intermediate between the two. 



The calcar (pre-hallux) attains, as is well known, its maximum 

 development in this family. Rosenhof first described and figured 



1 Tliia is not received by the ulnare, as might appear on examination of 

 the figure ; it lies, in life, ventrally to the line of junction between that bone 

 and the lunatum. It breaks away with great readiness, so much so that we 

 originally imagined it to be a distinct element. 



