238 



FOSSIL TURTLES OF NORTH AMERICA. 



has a height of 45 mm. All of these lie wholly on the peripherals. The fifth marginal 

 suddenly rises to a height of 100 mm. and overlaps the lower ends of the second and third 

 costal bones. The ninth marginal has a height of 145 mm. The next two are only slightly 



lower. The supracaudal scutes meet along the midline a dis- 

 tance of 97 mm. The costal scutes diminish in size from the first 

 to the last. The latter has a fore-and-aft length of 80 mm. and a 

 width of 55 mm. 



The plastron (plate 35, fig. 2; text-fig. 297), as in other spe- 

 cies of the genus, is relatively small. Both the anterior and the 

 posterior lobes are truncated. The total length {5355 mm. The 

 anterior lobe has a length of 80 mm. and a width of 175 mm. at 

 the base. The truncated anterior end is 85 mm. wide. The 

 entoplastron is 50 mm. long and 70 mm. wide. The bridges are 140 mm. wide. The posterior 

 lobe is 130 mm. long and 175 mm. wide at the base. The posterior truncated end is about 

 80 mm. wide. The free borders of both lobes are acute. The plastron articulates with the 

 peripherals by means of sutures; and axillary and inguinal buttresses rise nearly to the 



m.x.U 



FIG. 297. Adocus punctatus. Lower side of shell. Xo.i6. 



ab, abdominal scute ; an, anal scute ; r. />. I, c./>. z, etc., costal plates; ent, entoplastron ; epi, epiplastron ; fern, 

 femoral scute; g, gular scute; hum, humeral scute ; hyo, hyoplastron; hypo, hypoplastron; ig, intergular 

 scute ; infm, infrarnarginal scutes ; nu, nuchal bone; fee, pectoral scute; per. 3, per. 8, peripheral bones; 

 py, pygal; spy, suprapygal; xifh, siphiplastron. 



lower ends of the costal bones. Plate 34, fig. 5, from a drawing made for Dr. Baur, repre- 

 sents the upper side of the xiphiplastral bones. There are very distinct curved depressions 

 for the pubic bones, but there was no sutural articulation of the latter bones with the plastron. 

 The sutures between the various bones of the plastron are somewhat irregular, as is shown 

 in the figures. The sulci are still more irregular, especially the longitudinal median. All the 

 sulci are narrow and shallow. The intergulars have pushed the gulars away from contact at 

 the midline, and neither gulars nor intergulars overlap the entoplastron. The humerals occupy 

 42 mm. of the midline. The pectorals measure 40 mm. along the midline and they overlap the 

 hinder end of the entoplastron. The abdominals, the femorals, and the anals respectively 

 occupy 88 mm., 82 mm., and 72 mm. of the midline. There are 3 inframarginals on each of 

 the bridges. 



