and postorbitals, and form the ventral botindary of the 

 eye; the nasals, two plates surrounding the nostrils 

 and bordering dorsally on the prefrontals and inter- 

 nasals ; in some species these plates are fused into one, 

 in which case the nostril is said to "penetrate the 

 nasal plate"; the loreals, one on either side 

 between the preorbitals and nasals; the labials 

 (supralabials) , a long row of plates along the margin 

 of the upper jaw, the temporals vary in number in 

 different species, and are placed caudad of the post- 

 orbitals, between the parietals above and the 

 labials below. The number and arrangement of 

 these plates are employed in classification. For 

 example, the formula "temporals 1-2-2" indicates that 

 there are three (vertical) rows of temporals, and 

 that there is one plate in the first row behind the 

 postorbitals, and two in each of the other rows. 

 Write beneath the drawiag the formula for the 

 temporals of this species. The mental plate is 

 unpaired, and, placed at the tip of the lower jaw. 

 There are two pairs of submentals (geneials) directly 

 caudad of the mentals on the ventral side of the head. 

 The infralabials constitute a row along the edge of the 

 lower jaw caudad of the mental. The ventral plates 

 (abbreviated V. P. , and sometimes called gasterosteges) 

 are the large plates covering the ventral side of the 

 body. The one directly in front of the vent and 

 sometimes divided (bifid) , is called the anal plate. It 

 is usually cresentic in form. The plates caudad of 

 the vent on the vmder side of the tail are in pairs and 

 called urosteges. In some snakes they are not foimd 

 in pairs. The gulars are the small plates on the side 

 of the throat between the infralabials, submentals, 

 and ventrals. 

 Make a drawing of the ventral aspect in the region of 

 the vent, showing urosteges, ventral and anal scutes. 



(6). Make a drawing of the dorsum of the head. Label the 

 scutes. 



(7). Make a drawing of the left side of the head. The pit 

 located between the eye and the nostril is the 

 loreal pit. Compare the urosteges with those of No. i . 

 Result? 



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