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



Order, the Anura would appear to be unique among all living animals 

 in that they possess, without exception, a double centrale carpi. 



h, Gompoiind structures resulting from the fusion of two or more 

 Carpal elements. — Under this head we have designated certain large 

 bones, met with only in the adults of the more specialized families 

 and in some few isolated genera. 



There can be little doubt but that the great development of our 

 postaxial centrale (^) is associated with the peculiar " tread " of 

 the fore foot of the Anura and with the remarkable distortion which 

 the parts of this limb have undergone. In the compound 

 structures now to be dealt with, this postaxial centrale forms as it 

 were a central nucleus, towards which one or more adjacent elements 

 become drawn and with which they amalgamate. The fact that 

 the resulting compounds may occur independently in different 

 families is sufficient to show that they are, for the most part, of 

 nought but physiological significance. 



Capitatum. — We suggest this term ' for the simplest of the above- 

 named structures. It occurs in Pelodytes (fig. 11) and Pseiidophryne 

 (fig. 22) (4 k), being formed, as shown, by the confluence of the 

 postaxial centrale and the 4th carpal. 



Capitato-hamatum. — This term was applied by Ecker (see infra) 

 to a large bone which, in the Edible Frog (3. 4. k, fig. B, woodcut, 

 p. 1/4), carries the .3rd, 4th, and 5th digits. It is formed by the 

 confluence of our capitatum with the third carpal. 



We have observed it in the Banidce, Bendrobatidce, EngystomatidcB, 

 Cystignathidee, Bvfonidce, Hylidce, and certain others ; it is not 

 present in either the Discoglossidce, PelobatidcB, or Aglossa. It often 

 sends up, especially in old individuals, a process along the outer 

 face of the ulna (ex. Leptodactylus, fig. 25) for muscular attachment. 

 This lobe is absent in the tadpole, and, from its function, it need 

 hardly be said that it has nothing to do with articulation upon the 

 forearm ^. 



There sometimes runs along the under surface of this bone a 

 longitudinal groove, which terminates posteriorly, in a line with the 

 interspace between metacarpals 3 and 4. In old specimens this 

 becomes converted into a tubular perforation, which will admit a 

 bristle and transmits the ramus lateralis of the ulnar nerve ^ 



On examination of the adult carpus, doubts might be reasonably 

 entertained as to whether both third and fourth carpalia were incor- 

 porated in this piece. Apart, however, from the fact that in the 

 young animal their boundary lines are definable, there is a feature of 

 some interest in its mode of attachment. In Hyla ccerulea (fig. 20) 

 and Nototrema there still remains that ligament which, in the 

 simpler forms, passes between the 4th carpal and the head of the 

 5th metacarpal ; true to its relationships, it arises on a level with 

 the head of metacarpal 4 (cf. Xenophrys, fig. 14), and it differs from 



' Uniformly with Ecker's cajjitato-hamatum (17, p. 53). 

 ^ As might at first be imagined, from Wiedei-sheim's fig. oiiBiifo (36, pi. 211. 

 fig. 177), in which this feature is grossly exaggerated. 



' Of. iScker and Wiedersheim, ' Auat. d. Frosches,' part ii. p. 40 and fig. 14. 



