Recognition of Poisonous Snakes 



is important, and the fangs in tliese kinds are 

 quite long. 



Head Shields 



The size and arrangement of sliields on the top 

 and sides of the head are most helpful in snake 

 identification. In the great majority of snakes 



the top of the head is covered by large symmetri- 

 cal shields, typically 9 in number (see fig. 6). 

 Moi-e or less division of these shields into small 

 scales is seen in many kinds of vipers, many boas 

 and pythons, and in a few other kinds of snakes. 

 Reduction of the number through fusion of 

 shields is seen mostlv in small burrowing snakes. 



ROSTRAL 

 INTERNASALS 

 PREFRONTALS 



FRONTAL 



- PARIETALS 



_ SUPRAOCULARS 



POSTOCULARS 

 TEMPORALS 



ROSTRAL 



I UPPER LABIALS 



Figure 6. — Head of typical colubrid snake. ilhistratiiiK 

 arraiiKeraeiit of scales from dorsal and lateral views. 

 Any of these scales may be modified in shape or ab- 

 sent in v.arioiis };nmi)s of poisonous snakes. 



Figure .'j. — Skulls representative of vario\is families of 

 poisonous snakes, showing lengths of maxillary bones 

 (shaded) and positions and lengths of fangs. A. 

 Cobra (Elapidae). showing short fang in front part 

 of maxillary bone: B. Pit viper (Crotalidae). 

 .showing long fang on short maxillary bone; C. Rear- 

 fanged snake (Cohibridae), showing short fang on 

 rear part of long maxillary bone (Other parts of 

 skull diagrammatic only). 



If there are lypiial large shields on the crown 

 and no pit between the eye and nostril, look at 

 the side of the head in front of the eye. The 

 loreal siiield (see fig. (>) is absent in nearly all 

 ])oisonous snakes of the Elapidae as well as the 

 .\frican mole vipers ( Yii)eridae). This shield is 

 also lacking in a good many n()ni)oisonous snakes, 

 but many of these are small burrowers or strictly 

 aquatic snakes which may be eliminated on other 

 grounds. 'l"lie size of the eye may be important 

 (see GLOSS A PvY). 



Eye Characteristics 



The shape of the pupil of the eye should be 

 noted in live or freshly killed snakes. Most 

 snakes have round pupils, some have vertically 

 elliptical pupils, and a few have hoi'izontally 

 elliptical pupils. Vertically elliptical pupils are 



27 



