44 Eobert E. Coker. 



tioii, and structure. Terrapins display mucli individuality in these 

 respects. 



2. The diversity in number and arrangement of the scutes accords 

 with the general diversity. Of the first 243 specimens carefully 

 observ^ed, 20 per cent had either more or less than the typical 

 number of scutes in the carapace. In all, 45 per cent showed 

 such differences from the typical number, arrangement, and char- 

 acter of the scutes of carapace, plastron and inframarginal series, 

 as to be classed for present purposes as "abnormal." 



3. The "abnormalities" consist in : the possession of a greater 

 or less nimiber of scutes than 38 in the carapace, 2 in the infra- 

 marginal series, and 12 in the plastron; of instances of incomplete 

 fusion or incomplete division of normal or abnormal scutesi; of 

 asymmetry in size and plan of scutes ; of imbricateness of scutes ; 

 of the loose attachment of scutes to the bone beneath (one case). 



4. Asym/metry manifests itself in various ways, and is at least 

 as common in "abnormal" terrapins as symmetry. 



5. Females show a much greater degree of diversity than 7nales. 

 This is true as regards both percentages of abnormal individuals 

 and degree of abnormality in the average individual. 



6. 'No evidence was noted of difference in the proportions of 

 abnonnality in young and old terrapins, but the data are inadequate 

 for definite conclusion. 



1. The most variable scute is the inguinal. Typically absent, it 

 was present, on one or both sides, in 21 per cent of the 243 speci- 

 mens. Its approximately symmetrical occurrence was noted in 13 

 per cent of the 243. Karely, one or both axillaries were wanting. 

 Sometimes they were reduced in size or asymmetrical. 



8. The most variable scute of the carapace is the nuchal. Al- 

 ways present, it was sometimes paired, sometimes marked by a 

 median groove. 



9. Omitting the inframarginal series, the plastron is far less vari- 

 able than the carapace. Diversity manifested itself by the presence 

 of extra scutes in the plastral series and of inter-plastrals at the 

 meeting-point of gulars and brachials, by partial fusion of scutes, and 

 by asymmetry. Each abnormality is of rare occurrence. 



