82 ANIMAL LIFE PAST AND PRESENT. 



shown in the beautiful example represented in Fig. 23, 

 the contour of the soft parts of the paddles is accurately 

 delineated in the stony matrix. We thus see that the 

 fleshy part of the paddle formed but a comparatively 

 narrow band in advance of the bony framework on the 

 front border of the fin (right side of Figure) ; but on 

 the opposite or hinder border (left side of Figure) we 

 find the soft parts forming a broad fin-like expansion, 

 admirably adapted to obtain the full advantage of the 

 stroke of the limb in swimming. 



As we are on the subject of the paddles, we may 

 take the opportunity of noticing the very remarkable 

 structure of their bony framework, which is quite un- 

 like that found in any other animal, although evidently 

 only a modification of the same ground-plan. In most 

 of the higher vertebrates, as in man, the skeleton of 

 the arm, or fore-limb, presents the following features : 

 The upper-arm has one long single bone; in the 

 fore-arm there are two slender bones lying side by side 

 and separated by an interval ; the wrist has two rows 

 of small cuboidal bones ; while the limb terminates in 

 five fingers, of which, with the exception of the thumb, 

 each has three long-bones,* which are respectively 

 separated from the wrist by a similar but somewhat 

 longer bone. Turning to the fore paddle of the Fish- 

 Lizard (Fig. 23), we easily recognise in the topmost 

 bone (hu) the single bone of the upper- arm, although 

 this has become much shorter and thicker than is 



* In living reptiles the number of these bones differs in the indi- 

 vidual fingers, but never exceeds three in the second finger. 



