CHAPTER XIV. 



THE PELAGIC OR SEA SNAKES. 



THE modifications of ordinary forms which are seen 

 in the fresh-water snakes are still more beautifully 

 developed in the Hydrophidce, or true marine serpents. The 

 former, being never out of easy reach of shore, could easily 

 find a safe harbour from violent torrents, in holes in the 

 banks or among the strong aquatic weeds along the borders 

 of lakes and rivers ; and to be enabled to hold on to these in 

 times of danger or of repose, they possess a prehensile power 

 of tail. In a rough and stormy ocean, a much more powerful 

 propeller and rudder would be necessary for the guidance 

 of the reptile, and to afford resistance against the denser 

 medium of sea water ; therefore the tail of sea snakes is not 

 only prehensile but strongly compressed, so as to almost 

 form a vertical fin, answering altogether to that of a fish. 

 This is their most conspicuous and striking feature, and one 

 that w^ould leave no doubt in the mind of the observer 

 between the true marine and those fresh-water species which 

 may by accident drift out to sea by force of current. 



Another distineuishingf feature is the absence of ventral 



233 



