'202 THE STORY OF REPTILE LIFE. 



the figure, these became much shortened, so that 

 the forearm bones differ but little in size from 

 the wrist-bones in question. Still more note- 

 worthy is the relation of the digits one to 

 another, for they no longer remain separate 

 fingers and toes, but are so closely pressed 

 together that the separate joints have become 

 squeezed into a series of more or less hexagonal 

 plates interlocked to form a perfect mosaic an 

 arrangement unknown elsewhere among animals. 

 By a considerable addition to the number of the 

 finger bones or phalanges the length of the hand 

 has been greatly increased, whilst additional 

 width has been gained partly by adding a row 

 of bony nodules down the free border of the 

 innermost digits, and partly by a fold of skin, 

 which formed a kind of fringe around the paddle. 

 The fold along the hinder margin of the front 

 paddles at least was especially wide, and impres- 

 sions in the rocks of some of the best preserved 

 species show that in many cases it was stiffened 

 by a series of little rods resembling the fin spines 

 of fishes, like those supporting the fin running 

 round the plaice or sole, for example. In yet 

 other cases, additional width was gained by in- 

 creasing the number of the digits from five to 

 six. This was accomplished by splitting the 

 third digit. In some of the species which 

 appeared later in time, as in Ophthalmosaurus, 

 we find a considerable modification in the form 

 of these paddles. In the first place, the number 

 of the digits was reduced to four, whilst the 

 finger bones or phalanges exchanged their hexa- 

 gonal for an oval shape, and thus, becoming 



