136 WATER REPTILES OF THE PAST AND PRESENT 



tail was not only enormously elongated, but it was also compressed 

 into a Hat and effective propelling organ in the water. This 

 flattening of the tail is apparent from the skeleton, with its elongated 

 chevrons below and spines above, and it is also proved by the for- 

 tunate preservation of the extremity of the tail of one specimen, 

 showing not only the impressions of the scales in the matrLx, but 

 also the outUnes that the soft parts had in life. To quote from 

 Lortet, in translation: "The tail was covered wholly with small 

 scales, regularly hexagonal in shape, shining and nacreous, larger 



Fig. 64. — Life restoration of Pleurosaurns 



on the under side than above. The upper border of the tail was 

 surmounted by a broad crest, extending to its extremity, and com- 

 posed of large, oval scales." The body doubtless was wholly 

 covered with scales, though it is not probable that the caudal 

 crest continued along the back. 



The limbs begin to show an aquatic adaptation, though not 

 very pronounced. They are much shorter and smaller than are 

 those of land-crawling reptiles; and the bones of the second series, 

 that is, the radius and ulna, tibia and tibula, are relatively short, 

 the beginning of adaptation to water habits. It is very probable 

 that the feet were webbed, though the fifth digit, as usual, is shorter 

 than the fourth. Doubtless on land the creature moved about 



