12 Kobert E. Coker. 



Explanation of Tables. 



Abbreviations: "L," left; "R," right; "N," neural; "C," costal; "M," mar- 

 ginal. Thus "Nl" denotes the first (most anterior) neural, LC4, the fourth 

 (most posterior, tj'pically) left costal, etc. 



In the "inguinal column, "L" denotes the presence of a left inguinal, "R" 

 of a right, "L R" of both. If the left inguinal is distinctly larger than the 

 right, this is indicated thus "L > R," or, if the reverse is the case, "L < R." 



In the "Remarks" column "Supn'y" is used for supernumerary. 



In the "nuchal" column, "pr" indicates that the nuchal is represented by 

 a pair of scutes, "f," that it is marked by a longitudinal furrow, not dis- 

 tinguishable as a seam. 



The letter "x" in any column refers the reader to the "Remarks" column. 



In the "figures" column, letters refer to text figures, numbers to the figures 

 on the plates. 



Regarding the identification of scutes, it is not always clear to which 

 series in the carapace an anomalous scute should be referred, or in fact 

 whether there is reason in ascribing it to any normal series. But for con- 

 venience of description scutes will, when possible, be referred to normal 

 series. 



In dealing with forms of so high a market value as the diamond-back 

 teri'apin (Tables I to V) it was not always possible to retain the specimens 

 for further study. But in regard to scutes alone, revision of judgment is 

 necessary in a comparatively small number of cases, and a field sketch fre- 

 quently helps to remove this difficulty. 



Regarding the figures, some are photographs, some tracings from photo- 

 graphs, and some camera sketches, while others are field sketches (see Ex- 

 planation of Plates," etc.). No greater accuracy is claimed for the field 

 sketches than that they represent, somewhat diagrammatically, the position, 

 shape and proportionate size of the scutes depicted. 



As diversity manifests itself in so many respects, we must of necessity 

 disregard most individual differences, and consider only certain defined "ab- 

 normalities." In the tables that follow, a turtle is "normal," unless it pos- 

 sesses more or less than the number of scutes typical of the species, shows 

 instances of partial division or partial fusion of scutes, has a median plate 

 marked with a distinet and complete median groove, exhibits such asymmetry 

 as with one scute of a pair ttcice as large as its mate, or has scutes not 

 firmly united to the bone. 



