^^^<i EFFiiCTS (JF SXAKF \l<:i\(ms ON DO.Mi'ISTlC' ANIMALS. 



The two faiTiilies to which the ])oisonous ( Thanatophidia j 

 snakes belong are the ColubricUe and the Viperidae. In both of 

 these the central shields are so elongated transversel)' that their 

 ends can often be seen in a dorsal view, exce])t in the case of 

 some of the acjnatic Coltibridce. The CV(lnl)rid;e are identified by 

 the following features : — 



The head is covered b\' large, symmetrically arranged sliields. 

 The ventral shields are very much broadened transversely. The 

 maxilla is horizontal, and in many species carries a nnmljer of 

 teeth. The family is divided into three sections, according 

 to the form of the teeth, namely, Aijlypha. Opisflioglyplia, and 

 Protcroglypha. 



1. In the Aglvpha the maxilla is long, and carries numerous 

 teeth, none of which are grooved. All the Aglypha are harmless, 

 as not only is the special injecting apparatus absent, but the secre- 

 tions of those which uj) to the present have been investigated, have 

 proved innocuous when injected into small animals. 



2. In the Opisthoglypha the maxilla is long and carries many 

 teeth, of which a few of the posterior ones carry a longitudinal 

 groove on the anterior border, the groove being very open. This 

 family ])ossesses a gland which is homologous with the poison 

 gland of venomous snakes, and as the secretion is toxic for small 

 animals, the family must be looked upon as sus]iicious. 



3. In the Proteroglypha the maxilla is comparatively short, 

 and teeth are few. One or two of the anterior teeth in the maxilla 

 are very much enlarged, and constitute the poison fangs. 'Hiese 

 are so deeply grooved in son.ie cases as to ai)pear tubular. All this 

 family are poisonous, although, owing to the variations in to.x'citv 

 of the venom, death ma}^ not occur in all animals bitten. The base 

 of the ])oison fang is in coiumunication with a duct leading from 

 a highly specialised j)oison gland behind the orbit. 



The Proteroglypha Colubrines are subdivided into Hydro- 

 ])inae and Ela])in?e. These are distinguished bv the following 

 characteristics : 7die Hydroi:)inse are sea snake.s. the tail of which 

 is compressed like the blade of a i:)addle, and the ])oison fangs 

 are placed in the front of the up])er ja\\'. A few of the species 

 may be found on the shore, and in these it will be found that 

 the ventral shields are large, and the nostrils superior. The 

 venom of these Hvdropinae is extremely toxic, and is looked upon 

 as the most virulent known. 



In the other sub-family — the Elapinpe — the tail is of the ordi- 

 nary tapering cylindrical form. The head is covered with large 

 shields, and the central shields are enlarged transversely. 



The other family of the Thanatophidia — the Viperidse — is 

 distinguished by the short, freely movable maxilla, which is cap- 

 able of being erected into a perpendicular position, and carrying 

 large tubular poison fangs, which are the only teeth attached to 

 the maxilla. There is a bunch of unattached, small reserve poison 

 fangs immediately behind each main poison fang. It is customary 

 to suppose that the ViperidcC can be distinguished from the Cro- 

 talinge by the presence of a broad head covered with small scales, 



