176 



HISTORY OF THE HUMAN BODY 



named in order, beginning at the front, pro-, meso-, and meta- 

 pterygium (Fig. 46, A). These latter pieces have often been 

 considered as primitive, and various attempts have been made 

 to derive from them the long bones of the limbs in terrestrial 

 forms ; but they are not always found in ganoids, which ought 

 to show here, as elsewhere, transitions to the higher verte- 



Enton 

 Entale 



Stele 



Ecton 

 ,.ctale 



^ 



$ 



ii V 



*" 



IV 



in 



FIG. 47. Diagrams of typical free limb skeleton. 



(A) According to the usual nomenclature; names belonging to the posterior limb 

 are bracketed. (B) Suggestion for a common nomenclature for both limbs. 



In (A) the separate carpal and tarsal pieces are as follows: a, radiale [tibiale] ; 

 b, ulnare [fibulare]; x, intermedium; y, centrale; i 5, carpalia [tarsalia]. 



In both diagrams the more constant sesamoids are indicated by dotted lines. 



brates. The Dipnoi show a beautifully symmetrical type of 

 fin-skeleton, which consists of a jointed central axis with rays 

 upon either side, a type which many have regarded as the 

 primitive form from which all the other cases have been de- 

 rived, and have named it accordingly the archipterygium 

 (Fig. 46, B). The highly specialized Dipnoi, however, are 

 not the proper animals to which to look for primitive condi- 



