562 



MERIST1C VARIATION. 



[part I. 



EC 



TV 



Fig. 207. Chrysemys picta, 2 or 3 days old. I, II, normal. Ill and IV, two- 

 headed specimen. In the latter the nuchal and two pygal plates are normal. Be- 

 tween them are 12 plates on each side, 11 being the most usual number. Among 

 the costals an extra plate is wedged in on the rt. First vertebral divided by suture ; 

 fifth is made up of 4 irregular plates. In the plastron there is a doubling of the 

 gular plate. The rt. femoral has a suture. (From Barbour.) 



