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PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 59. 



num^ (Cope) from this same formation, as exposed near Montezuma, 

 Macon County, Georgia. 



The sulci defining the first vertebral scute and the costo-marginal 

 contact are the only ones that can be traced, though the sutures 

 between the bones can nearly all be clearly made out as shown in 

 figure 5. 



The shell, both carapace and plastron, are thick and heavy. The 

 free border in front, is obtuse and flares upward. The nuchal plate 

 has a length antero-posteriorly of 52 millimeters; a greatest width 

 of about 64 millimeters. The neurals are especially elongated, 

 hexagonal in shape, with the widest end forward, all being longer 

 than wide, whereas in A. oxy sternum they are wider than long. The 

 principal dimensions of the neurals are given in the table. 



Measurements of neutrals, in millimeters. 



« Estimated. 



The fii-st costal has a gi'eatest length of 92 millimeters, a width of 

 72 millimeters; the second is 100 millimeters long, and 42 millimeters 

 wide at the proximal end; third is 120 millimeters long, and 44 

 millimeters wide at proximal end; fourth 126 millimetei-s long, and 

 42 millimeters wide; fifth is about 125 millimeters long. Excepting 

 the first, the other costals present in the type are remarkably uniform 

 in the widths of the proximal and distal ends. 



The peripherals are high and all unite closely and strongly by 

 suture with the distal ends of the costals. At about their centers 

 they are crossed by the costo-marginal sulcus. On the ventral side 

 of this sulcus the bone swells abruptly outward forming a prominent 

 offset along the side of the shell, but not a ridge as in the genus 

 Hoplochelys. Peripheral 6 has a width fore and aft of 42 millimeters; 

 7 is 43 millimeters wide. 



The surface of the shell is without ornamentation, except for a 

 broad rounded median longitudinal keel which is paralleled on each 

 side, at a distance of 35 millimeters, by lateral keels. The median 

 keel appeai-s to rise close to the anterior border of the nuchal plate. 

 These keels resemble somewhat those found on the carapace of 

 Hoflochelys saliens Hay, but are less prominent, being lower and 

 more rounded, as contrasted with the higher and sharper keels of that 

 species. 



» See Hay, O. P., Fossil Turtles of North America, 1908, p. 256, flg. 256. 



