424 



FOSSIL TURTLES OF NORTH AMERICA. 



The nuchal bone occupies 140 mm. of the free border and is 182 mm. wide at the widest 

 portion; 141 mm. long in the midline. Its greatest thickness at the midhne is 36 mm. The 

 bridge peripherals are very high, about 230 mm. and therefore nearly as high as the costals, 

 the fourth of which is 257 mm. high. The thickness of the inner surface of the hinder periph- 

 erals increases to about half of the 

 height and is then suddenly reduced, 

 the maximum being about 23 mm. 

 The pygal is 80 mm. wide at the 

 free border, 114 mm. at the upper 

 border and 83 mm. high in the mid- 

 line. Its thickness at the midline is 

 24 mm. 



The second costal is 70 mm. wide 

 near the proximal end, 88 mm. at 

 the distal end. The third is 100 mm. 

 FIG. 554- Testudo osborniana. Skull of type, w i<] e at tne p rox imal end, 70 mm. at 



right side. X . t he distal end. The fourth has a 



width of 68 mm. at the proximal end. 90 at the distal end. The fifth has the dimensions respec- 

 tively 83 mm. and 76 mm. The sixth is 73 mm. wide proximally, 102 distally. The seventh is 

 48 mm. across the proximal end, 93 across the distal. It is seen from these figures that, as 

 in other species of Testudo, the costals, omitting the first, are alternately widened and nar- 

 rowed proximally, whilst alternately narrowed and widened at the distal ends. The degree 

 of differentiation among the costals is, however, less than is usual in the genus. 

 The neural bones have the dimensions given in the table below. 



The first suprapygal is 93 mm. long at the midline, 40 mm. wide at the upper end, and 

 183 mm. at the lower, the bone having the usual notch in its lower, or hinder, border. The 

 second suprapygal has a median length of 69 mm. and a width of 92 mm. 



The vertebral scutes are large, the dimensions being shown in the table. 

 The nuchal is small, being 27 mm. wide at the anterior end, 1 1 mm. at the hinder end, and 

 52 mm. long. The supracaudal scute is 225 mm. from side to side, and has a height of 102 mm. 



The anterior lip of the plastron (plate 73; 

 text-fig. 556) is greatly developt. At its base, 

 where the sulci bounding the gular scutes 

 cross the free border, the width of the lip is 

 205 mm. The front of the lip is slightly notcht 

 in the midline. From this the subacute 

 border curves round to the base of the lip. 

 From the free border the bone thickens rap- 

 idly backward for a distance of 135 mm. until 

 it reaches a thickness, in the midline, of 75 

 mm. The thickness then drops suddenly off 

 to that of the greater portion of the plastron. 

 The escarpment of bone thus formed is very 

 slightly excavated. The free border of the anterior lobe behind the lip is acute. 



The hinder lobe of the plastron has a wide shallow notch behind. The width of the notch 

 is 130 mm.; its depth is only 23 mm. 



The entoplastron is 153 mm. fore and aft, and 210 mm. wide. The hyoplastra extend 

 140 mm. along the midline; the hypoplastra, 160 mm.; and the xiphiplastra, 127 mm. The 

 free border of the hinder lobe is subacute. From the border the bone thickens rapidly. Toward 

 the inguinal notch the border rises and forms a wall which reaches a height of 80 mm. Its 

 summit is narrow, and the slope on the mesial side is abrupt. 



The gular scutes occupy 170 mm. of the midline; the humerals, loo mm.; the pectorals 



only 10 mm.; the abdominals, 255 mm.; the femorals, 76 mm.; and the anals, 85 mm. 



The pelvis is in its natural position and is complete, except that the anterior processes 



of the pubes are missing. The processes on the hinder border of the ischia resemble those of 



