Diversity in the Scutes of Chelonia. A'.) 



4. Age^ Sex^ Symmetry. 



Age. 



It was shown in a previous paper ('05 a) that my observations 

 do not indicate any significant difference in the proportions of 

 abnormality at different ages. The cases of incomplete division 

 and incomplete fusion noted all seem to tend toward increasing 

 the abnormality in 7iumher of scutes. Newmann ('06), after exam- 

 ination of nearly 500 specimens of Graptemys, including a number 

 of embryos, finds that "abnormalities are no more common in one 

 size than in another." lie notes, however, some cases interpreted 

 as stages in the squeezing off of scutes (cf., my specimens No. 50, 

 p. 22, 23). 



Sex. 



The proportion of abnormality in the females of tables I to IV 



is noticeably greater than that in the males. Considering all the 



abnormalities of carapace and plastron, as defined on p. 12, above, 



24 out of Yl males are abnormal, or. 34 per cent, and 71 of 135 



females, or 52.6 per cent. Of 37 the -sex is not known. Of the 



entire 243, 109, or 45 per cent are abnormal. If, however, w^e 



consider only the possession of more or less than the typical number 



of scutes in the carapace, the proportion of abnormality is about 



20 per cent. 



Symmetry. 



51 specimens show only symmetrical abnormalities. 



44 specimens show only non-symmetrical abnormalities. 



14 specimens show both kinds of abnormalities. 



Thus, of the 109 abnormal turtles of tables I to IV, 51 are sym- 

 metrical, 58 unsymmetrical, in the respect that we have taken into 

 consideration. 



Before taking up the embryos and young of ThalassocJielys it will 

 be well to give a summary of the observations on Malaclemmys. 



Summary. 

 1. Observation of diamond-back terrapin in nature and in con- 

 finement reveals a marked degree of diversity in habit, disposi- 



