154 OPHIDIA. 



hissing, and filled the room with such nauseous 

 effluvia, as rendered it hardly supportable."* 



The eggs of serpents are enclosed in a calca- 

 reous covering, which is not hard and shelly, but 

 tough, somewhat resembling kid-leather, or wet 

 parchment. They are often numerous, and are 

 deposited together, and connected by a sort of 

 glutinous matter. Holes in the earth, in dung- 

 hills, or in heaps of decaying vegetable matter, 

 are situations frequently chosen for their recep- 

 tion ; and here they are left to be hatched by the 

 heat of the weather, or by that which is developed 

 in the putrefactive fermentation of the surround- 

 ing mass. The venomous species, as far as we 

 are acquainted with their habits, are ovo-vivipa- 

 rous, the membrane of the egg being ruptured 

 either before or during parturition. 



We have said that the instruments of progres- 

 sive motion in the Serpent tribes are the multi- 

 tudinous ribs. The vertebrae of the spine admit 

 of excessive flexibility, and the ribs are jointed 

 upon them in a manner which allows the latter 

 an extent of motion unusually great. The mode 

 in which a Serpent proceeds will be understood 

 from the following observations, the reader bear- 

 ing in mind that the whole under surface of the 

 body is shod, as it were, with broad plates, or 

 scuta, the hinder margins of which are free. 

 " When the Snake," says Sir Everard Home, 

 " begins to put itself in motion, the ribs of the 

 opposite sides are drawn apart from each other, 

 and the small, cartilages at the end of them are 

 bent upon the upper surfaces of the abdominal 

 scuta, on which the ends of the ribs rest ; and 



* Letter XXV. (1st series.) 



