FOSSIL REPTILES. 373 



more pointed fins. The humerus and femur are at first cylin- 

 drical, terminated above by a convex head, without neck or 

 tuberosities, flatted and widened below. Nevertheless, the 

 humerus is distinguished from the femur, because it is more 

 flatted towards the bottom, and its external edge forms a more 

 concave curve. 



The bones of the fore-arm and those of the leg are short 

 and broad, and almost alike in both limbs. One of the two 

 thickest of these bones is narrowed in the middle ; the other 

 is flatted, and its external edge presents the arch of a circle. 

 In the leg this flat bone represents the fibula, and is there 

 a little emarginated at this external edge. In the fore-arm it 

 represents the radius. 



We then find some flat and round bones, which represent 

 the carpus and tarsus. 



To the carpus there are but four bones in the first rank, one 

 of which, a little outwards, is the os pisciforme. There are 

 three in the second. To the tarsus, it appears that there were 

 in all but six, the two largest of which, probably, represent the 

 astragalus, and the calcaneum of the lizards. 



All the rest of the fin or paddle is formed by the metatar- 

 sians and the phalanges, very obviously disposed in five longi- 

 tudinal series which represent the five toes ; but the phalanges, 

 as in the fin of whales, are in much greater number than 

 usual. 



There are, at least, seven in the second and third of the 

 fore-toes, which are the longest; and, at least, ten upon the 

 third toe of the hinder extremity. The absolute numbers of 

 all are, however, difficult to state, because some small phalanx 

 may be lost, especially on the lateral toes. The shortest ap- 

 pears to have been the thumb, which does not seem to have 

 had more than four or five articulations, comprising the meta- 

 carpian or metatarsian. 



All these little bones are united by synchondrosis, as in the 

 cetacea, rather than by articulations, admitting freedom of 



