20 Kobert E. Coker. 



Part I. Malaclemmys. 

 The observations are presented as made on individual specimens in 

 the tables of Section 1, and are treated in classified form in Section 

 2. The classification of abnormal neurals and costals leads to the dis- 

 cussion of adjustment of neurals and costals which forms the sub- 

 ject of Section 3. 



1. Observations. 



The first 243 specimens that could be observed carefully are 

 included in Tables I to IV. These tables may, therefore, give a fair 

 idea of the proportion of "abnormal" individuals in this species. 



Table V includes a few specimens that were selected from a con- 

 siderable number of others that have come under observation. 



2. Review of Observations.^ 

 Inframarginals. 



The inguinals are by far the most common scutes not typical of 

 the shield of this species. JSFo less than 21 per cent of the 243 speci- 

 mens possessed one or both inguinals. In 33 individuals inguinals 

 were present on both sides (v. Figs. D and E), but in 4 of these 

 a distinct difference in size was noted between the scutes of the pair. 

 Seventeen specimens had inguinals on only one side (Fig. F). 

 Axillaries were wanting in only one terrapin, but were quite small 

 in two others. In 5 specimens one axillary was wanting (Fig. L), 

 and in 4 others one scute was at least twice as large as its mate of 

 the opposite side (Fig. 4). Another individual (jSTb. 114) had 

 axillaries of normal appearance, but they were found to be loosely 

 attached to the bone beneath, the skin connecting them with the 

 adjacent scutes permitting a certain freedom of movement when the 

 axillaries were pressed with the finger. It may be noted from the 

 tables that a right inguinal occurred alone 12 times as opposed 

 to 5 instances of the left alone, and the right was distinctly larger 

 than the left 3 times as against a larger left once ; also, while the 

 right axillary occurred without the left 5 times, the left without 

 the right was not noted. The right axillary was twice as large as the 



"Numbers and percentages refer to Tables I to IV, unless otherwise stated. 



