36 Robert E. Coker. 



In the endeavor to make clear the inferred law of growth, I have, 

 in a measure, proceeded in anticipation of the evidence from which 

 the inference was made. The body of the evidence may now be 

 best presented, not by detailed discussion, but by reference to text- 

 figure P, in which are indicated the neurals and costals of a number 

 of specimens. I have drawn freely on Newmann's figures, as his 

 observations include more specimens bearing on this particular 

 point than do my observations on Malaclemmys. My observations on 

 another species need not be introduced at this point. 



Each carapace figured may be compared, on the one hand, with 

 the types Fig. ]^, I and II, and on the other hand, with that of 

 Fig. K, III, or Fig. O, III c, and III, d. 



It is readily observed that there is no correspondence between the 

 number of extra costals and number of extra neurals, but that the 

 region of "abnormality" in the neural series corresponds in antero- 

 posterior extent with the region of asymmetry in the costal region. 

 If asymmetry of costals is confined to a small region, the adjust- 

 ment of neurals may require only one or two supernumerary ele- 

 ments (cf. Fig. P — V, VI, VII, etc.) ; but when asymmetry marks 

 a larger part of the costal region the adjustmient of the neural in- 

 s^olves two, three, or more elements in excess of the normal number 

 (cf. Fig. P— I, II, III, IV). 



A few cases which may be classed as partial or complete excep- 

 tions require discussion. These are included in Fig. Q, to which 

 refer the Roman numerals in the following paragraphs: 



The carapace figured in VI illustrates in part the adjustment 

 supposed. The adjustment would be complete only if a seam united 

 the apices of RC4 and LC5. On any hypothesis this is a remark- 

 ably abnormal shield. (From l^ewmann's Fig. 9.) 



In VII there are 5 costals on each side, but the number of neurals 

 is normal. However, the mesial region of the two costal series are 



'The nuchal and the marginals are omitted in most cases, since they have 

 no bearing on the point in question, and would only complicate the figures. 

 In the subscription full references are supplied, so that the original figures 

 may be consulted if it is desired. 



