40 



GUIDE TO REPTILES AND AMPHIBIANS. 



and ulna of the front-paddle (like the tibia and fibula in the hind- 

 limb) are elongated and separated by a wide cleft, while the other 

 bones of the paddles are also somewhat elongated, often notched on 



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one or both borders, and arranged in three rows. In Ichtliyosmirtis 

 (347, 348), on the other hand, the radius and ulna are transversely 

 expanded and in apposition, while the other bones of the paddle are 

 also very short and broad, and the ribs are two-headed. In certain 

 species, the paddle-bones are arranged in three longitudinal rows. 



