156 OPHIDIA. 



this kind of progressive motion." " An 



observation of Sir Joseph Banks during the ex- 

 hibition of a Coluber of unusual size first led to 

 this discovery. While it was moving briskly 

 along the carpet, he said he thought he saw the 

 ribs come forward in succession, like the feet of a 

 caterpillar. This remark led me to examine the 

 animal's motion with more accuracy, and on put- 

 ting the hand under its belly, while the Snake 

 was in the act of passing over the palm, the ends 

 of the ribs were distinctly felt pressing upon the 

 surface in regular succession, so as to leave no 

 doubt of the ribs forming so many pairs of levers, 

 by which the animal moves its body from place to 

 place." 



It is doubtless by the expansion of these rib- 

 feet, and by the application of them alternately 

 to the surface on which they move, that Serpents 

 are able to glide with facility up the trunks, and 

 along the branches of trees, a feat which *ve have 

 seen the Coluhridce of America and the West 

 Indies perform repeatedly, not (as absurdly repre- 

 sented in engravings) by encircling the tree in 

 spiral coils, but gliding along with the body ex- 

 tended, exactly as a caterpillar crawls, but with 

 far greater speed. 



The earth is the sphere of activity of by far the 

 greatest number of the Serpent races : they in- 

 habit various situations, some frequenting woods, 

 others heaths, and many preferring deserted 

 buildings, old walls, and heaps of stones. A few 

 species reside permanently among the foliage of 

 trees ; and others there are, which are truly aqua- 

 tic, roving through the ocean even at consider- 

 able distance from the shores. These have the 



