612 REPTILIA. 



The British adder (PeJias herus} is viviparous, and so are a few others. 

 The great majority are oviparous, but confinement and abnormal con- 

 ditions may make oviparous forms, like the Boa constrictor and the 

 British grass-snake ( Tropidonotus na/rix], viviparous. The female 

 python incubates the 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, though there can be little doubt that the snakes are often 

 innocent scapegoats. 



True Ophidians first occur in Tertiary strata. 



Some Examples of Ophidia. 



Typhlopidre. 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. Typ/itops, 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 (CoroneUa hcvis) ; the 

 British grass snake ( Tropidonotns 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. 

 Examples. Cobras, Naja tripitdians (Indian), Naja haje 

 (African) ; the Hamadryad (Ophiophagns elaps), eating 

 other snakes; Coral-snakes (Elaps, etc.); Sea-snakes 

 (Hydrophis, etc.), with paddle-shaped tails. The British 

 adder (Pelias bents] ; the rattlesnake (Crotahts), with a rattle 

 formed chiefly from epidermic remnants of successive slough- 

 ings ; the African Puff-adder (Clotho arietans}. 



