634 REPTILIA. 



is much elongated; the kidneys are not opposite one 

 another. 



The poison is useful in defence, and in killing the prey, 

 which is always swallowed whole. It is interesting to notice 

 a recent discovery, requiring amplification, that the bile of 

 a poisonous snake is an antidote to its venom. 



The British adder (Pelias berus] is viviparous, and so are a few 

 others. The great majority are oviparous, but confinement and 

 abnormal conditions may make oviparous forms, like the Boa con- 

 strictor and the British grass-snake ( Tropidonotus natrix], viviparous. 

 The female python incubates its eggs. 



Many Ophidians become lethargic during extremes of temperature, 

 or after a heavy meal. 



Snakes are especially abundant in the tropics, but occur in most 

 parts of the world. They are absent from many islands ; thus there 

 are none in New Zealand, and we all know that there are no snakes 

 in Iceland. Most are terrestrial, but not a few readily take to the 

 water, and there are many habitual sea-serpents. 



The serpent still bites the heel of progressive man, the number of 

 deaths from snake-bite in India alone amounting to many thousands 

 yearly. 



True Ophidians first occur in Tertiary strata. 



Some Examples of Ophidia- 



Typhlopidae. The lowest and most divergent Ophidians, occurring 

 in most of the warmer parts of the earth, generally smaller than 

 earthworms, usually subterranean burrowers, with eyes hidden 

 under scales, with a non-distensible mouth, with teeth restricted 

 either to the upper or to the lower jaw. "The palatine bones 

 meet, or nearly meet, in the base of the skull, and their long axes 

 are transverse ; there is no transverse bone ; the pterygoids are not 

 connected with the quadrates." The quadrate articulates with the 

 pro-otic, for there is no squamosal. 



Example. Typhlops, very widely distributed. 



In other Ophidians the palatines are widely separated, and their 

 long axes are longitudinal ; there are transverse bones connecting 

 palatines and maxillae; the pterygoids are connected with the 

 quadrates. 



In innocuous snakes the poison gland is not developed as such ; the 

 maxillary teeth are not grooved. 



Examples. The British smooth snake (Corontlla Itzvz's) ; the 

 British grass - snake ( Tropidonotus natrix} ; the Pythons ; 

 the Boas, of which the Anaconda (Boa murina} (30 feet) is 

 the largest living Ophidian. 



In venomous snakes some of the maxillary teeth are grooved, and in 

 the most venomous the groove becomes a canal open at both ends. 



