Poisonous Snalces o^ the World 



fhiiriii'h'risi u' of iiiosl vipoi's Itiil somo iioiipoisoii- 

 mis sniiki's also liiivo tliis typo. Most vt'iionioiis 

 clnpiils Imvo roiiml pupils. 



Dorsal Scale Characteristics 



'riio mmilii'i- ot" (loisai scalp rows is somctinips 

 important in siiako iiUMititicatioii. 'rii(> iiicthod of 

 countiiifj is shown in lii;nn' 7. A\'liili' ii is i|uilt' 

 |i()ssil)lt> to niako this count on a snako "in the 

 louml" so to si)t'ak, the incxpeficnccd individual 

 may obtain better fesidts by skinninir out a sec- 

 tion of the body and flal(cnin<i; the skin. It is 

 seldom possible to take a satisfactory scale count 

 of a live snake. It is often desirable to note if 



FiGtRK 7. — Method of fouiiting dorsal scale rows. Fig- 

 ure drawn as though skin has been slit down belly 

 and spread flat (V = ventral plates). 



the dorsal scales have a loiie^itudinal raised ridge, 

 kee/ed. or if they lack such ridges, funooth (see 

 fig. 8). 



form of I lie tail is often impoitanl in idcnliflca- 

 I ion \irlually (li;io-|i(isl ic in sea snakes and 

 ral I ji'siiakes. 'riic. suln-anija I miiIcs are ii anally in 

 a (ioiii)ie row (paired) ; liowe\er, in som(^ species, 

 all or most may bt^ in a siiigh^ row (see ligur<i 10). 

 A couhl of iIk^ subcaudals is I'oul inc. 



Sex 



Sex of a snake can sometimes b(^ dclermined 

 readily by oiiserving eggs or (le\-eloping young in 

 liu' oviducts. Pressure by lingers oi' iiijeclion of 

 liquid at liie bas(^ of the tail will usually evert, 

 the copulatory organs or hemipenes of a male 

 snake. The morphology of these organs is im- 

 portant in snake taxonomy. T'sually they are 



Ventral Scutes 



In the vast majority of snakes, large transverse 

 scutes extend the full width of the belly. These 

 are considerably reduced in size in boas and 

 pythons, some freshwater and burrowing snakes, 

 and in many sea snakes (see figure 9). They are 

 completely absent in the burrowing blind snakes, 

 aird iir some sea snakes. A complete count of 

 the ventrals is routine procedure in systematic 

 herpetology. It is easily done, but rather tedious, 

 and is not required for most of the species identi- 

 fications in this manual. 



Tail 



The tail of a snake begins at the anal plate 

 which covers the opening of the cloaca. The 



C^ir^tK^ 



Figure 8. — Figures of dorsal scales showing major 

 types of scale ornamentation : A. smooth scales. B. 

 keeled scales. 



28 



