158 PROF. G. B. HOWES AND ■W. RIDEWOOD ON [Mar. 6, 



his obserTation be reliable, this supposed centrals ought to be forth- 

 coming in younger specimens as a distinct element. We have 

 examined a large series of specimens, many of which were much 

 younger than any which passed through Bom's liands, and they 

 showed without exception that the position of his " centrale " was 

 occupied by the preaxial third of that element regarded by us as the 

 postaxial centrale {k, fig. 9). We can confidently assert that in no 

 carpus under our hands does this show a trace of either segmentation 

 into two, chondrification from two centres, or confluence of distinct 

 elements \ 



In one specimen we have been able to detect a linear depression on 

 the under surface of the cartilage, near the point at which Bom's 

 dismemberment appears to have occurred" ; and we are strongly of 

 opinion that this groove was present in his specimen, and that the 

 section rej)resented " by him passed tlirough it. Indeed, his second 

 assertion above cited seems, in itself, to coafirin this belief. 



In the adults of certain forms the naviculare may lie, as already 

 said, more or less completely in the proximal row, preaxially to the 

 lunatum and in more or less definite articulation with the radius 

 {cf. figs. 6, 18, 30). In others it may be as fully removed from the 

 latter (figs. 1, 5, 7). It therefore becomes a question of vital 

 importance as to which of these two conditions is the more primi- 

 tive. 



In examining a large series of larvse of the Edible Frog, measuring 

 each about 20 mm. from snout to vent, we were not a little surprised to 

 find that the naviculare varied greatly in the extent to which it thus 

 embraces, as it were, the lunatum. In the adult it comes to lie in 

 the proximal row, nearly meeting the radius {n, woodcut fig. B, 

 p. 174). In a young Bufo of about 20 mm. it was already in 

 direct apposition with this bone. In Pipa (Plate VII. fig. 1), Xenopus 

 (Plate VII. fig. A), and most Hylidce (Plate VIII. fig. 20) it is 

 strictly central; in one member of the last-named family however 

 (Nototrema) it shows a tendency to become proximal in the adult. 



In the adult oi Bombinator (Plate VII. fig. 7), and still more so in 

 that of Discoglossus (fig. 6), it sends up a spur which approaches 

 but does not nearly reach the radius. Appeal to development shows 

 (figs. 5 & 9) that this spur is a late growth. 



The condition of the jjarts in the Felobafidce is deserving of special 

 note. It will be seen that in those Anura in which the naviculare 

 is most central in position the distal carpals are relatively small and 

 reduced ; in Xenoplirys (fig. 14) and Pelobates (fig. 1 8) these are, on 

 the contrary, larger and more nearly uniform in size with the other 

 elements of the carpus, so much so in the latter genus that the carpus 

 has quite a Salamandrine aspect. Here too the naviculare is proximal 



^ Ossiflcatiou of this element invariiibly proceeds from one centre. 



- This becomes still more marked in certain forma in which our postaxial 

 centrale is confluent with olher elements {cf. p. 160). 



^ There are other exceptional peculiarities about this carpus, for which vre 

 find no parallel in our own specimens. 



