Vol. I] VAN DENBURGH-GIGANTIC LAND TORTOISES 5 



Diagnosis. — No nuchal; gulars paired; fourth cervical vertebra 

 biconvex; front of carapace high, not lower than middle, height at 

 nuchal notch more than 41% (54%) of straight length; difference 

 between percentages of height at third vertebral and at nuchal 

 notch less than 9 (2); carapace saddle-shaped, narrow anteriorly, 

 width at margin of junction of second and third marginals not more 

 than 54% (46%); first marginals much enlarged, everted more than 

 in any other race, their ventral surfaces nearly vertical, their edges 

 from nuchal notch to prominent point nearly horizontal, prominent 

 point almost a right angle; distance between prominent points of 

 first marginals more than 30% (32%); length over curve more than 

 123% (124%), greater than width over curve; vertical distance from 

 lower surface of plastron to lower edge of lateral marginals small, 

 6%; general size moderate, straight length 34.5 inches; plastron 

 short, 70% ; pectoral plates forming a suture on median line ; lower 

 jaw and throat marked with yellow. 



A few words in explanation of the measurements given in 

 the foregoing descriptions may be necessary. In attempting 

 to avoid the indefiniteness which has too largely characterized 

 descriptions of these tortoises it was quickly found necessary 

 to devise some means of expressing and comparing upon paper 

 their individual variation in shape. This, it was found, could 

 best be done by taking numerous measurements of each tor- 

 toise and reducing all these measurements to percentages of 

 the (straight) length of the tortoise. In this way, the measure- 

 ments of tortoises of all sizes may be directly compared. The 

 tortoise is placed upon a level board or table in such a position 

 that it rests naturally upon, as nearly as possible, the entire 

 length of the plastral bridge of each side. With the tortoise 

 in this position, the straight length is the distance between 

 verticals erected at the nuchal notch and at the posterior 

 border of the supracaudal plate. The straight width is the 

 distance between verticals erected at the sides of the tortoise 

 opposite the line of meeting of the second and third costal 

 plates. The curved length is measured with a tape-measure 

 over the midvertebral line from the nuchal notch to the pos- 

 terior edge of the supracaudal plate. The curved width is 

 taken from the bend in the marginal plates up along the line 

 of meeting of the second and third costals, across the middle 

 of the third vertebral, down between the second and third 

 costals, to the line of bending of the marginals. The width 



