476 PEOF. ST. GEOEGE MIVAE.T ON THE 



This view may be represented (with, respect to the arm and hand) as in the annexed 

 diagram : — 



Fig. 5. 



A 



"^ J7\. ^i^" 



//iX\ 

 // i V %' 



18 



f B \ 



1, humerus ; 2, intermedium (lunare) ; 3, centrale ; 4, magnum ; 5, 6, 7, & 8, metacarpal, and then pha- 

 langes of middle digit; 9, radius; 10, radiale (scaphoid); 11, trapezium : 12, 13, 14, metacarpal and pha- 

 langes of poUex ; 15, trapezoides ; 16, 17, 18, 19, metacarpal and phalanges of index digit ; 20, median half 

 of unoiforme; 21, 22, 23, and 24, metacarpal and phalanges of fourth digit ; 25, ulna ; 26, ulnare (cunei- 

 forme); 27, external half of unciforme ; 28, 29, 30, and 31, metacarpal and phalanges of the fifth digit. 



As Professor Huxley truly says ^ : — " The confirmation or refutation of this hypo- 

 thesis is to be sought in development, and in the condition of the limbs in the 

 Palaeozoic Amphibia." And he tells us that his suggestion is made " mainly in the 

 hope of stimulating investigation in both these directions." 



Professor Huxley's view is, I consider, the best yet suggested ; but I cannot feel 

 much confidence in its acciuacy for all that. I cannot do so on account of the poly- 

 morphic nature of the Elasmobranch fins, the multitudinous diflferences of which seem 

 to point to protean transformations, and therefore to an extreme plasticity, which may 

 have generated the cheiropterygium from any one of numerous possible sources. More- 

 over Professor Huxley's view seems to demand the unity of the centrale, while this 

 carpal ossicle, deemed double by Gegenbaur in Iclithyosaiirns and Plesiosmirus, has now 

 been shown to be actually double, not only in Cryptobranchus, but in both limbs of three 

 species of Siberian Urodeles ^, while the representations given in the memoir referred 

 to certainly do exhibit the tarsal and carpal structures rather as portions of oblique 

 rays, proceeding radiad and distad from the ulnar side of the limb, than as disposed 

 in harmony with Professor Huxley's hypothesis. 



' P. Z. S. 1876, page 57. 



' Namely, in Banodon sibiricus, Salamandrella heyserlingii, and SulamandreUa icosnefsenskyi. See Morpho- 

 log. Jahrbuch, vol. ii. 3rd Heft, page 421, and plate xsix. : " Die altesteu Formen des Carpus und Tarsus 

 dcr heutigen Amphibien," by Dr. E. Wiedersheim. 



