3 10 



KOSSII, TURTI.KS OF NORTH AMKR1CA. 



been about 250 mm. The anterior border is truncated. The free margins are nowhere 

 notcht. The nuchal is 50 mm. long, 43 mm. wide in front, and 75 mm. where widest. Its 

 anterior border, as well as that of the peripherals of the first pair, is acute. These bones are 

 rather thin, only 1 1 mm. The anterior and the posterior neurals are relatively broad, the 

 others narrow. The dimensions of the neurals are shown in the table. 



The fifth neural is octagonal, due doubtless to an individual variation. The first supra- 

 pygal is 22 mm. long and 33 mm. wide. 



The costal plates are usually about as wide at the upper end as at the distal end. However, 

 the third is 37 mm. wide proximally and 27 mm. distally. The third has a height equal to only 



394- 



395- 



FIGS. 394 AND 395. Echmatemys wyomingensts. Carapace and plastron. X}. 



No. 5988 A. M.N. H. 



394. Carapace. 



395. Plastron. 



41 per cent, of the height of the first costal near its hinder border. The posterior peripherals 

 possess an acute free border. The first costal bone is hardly two-thirds as wide as high. 



The dimensions of the peripherals are given in the table above. 



The sulci are narrow and rather shallow. The first and fifth vertebral scutes are broad, 

 the others are narrow, with nearly parallel sides. The dimensions of the vertebral scutes 

 are shown in tabular form above. 



The costo-marginal sulci run about 16 mm. below the costo-peripheral sutures. 



The plastron (plate 47, fig. I ; text-fig. 395) is 304 mm. long. It is thick, especially at the 

 crossing of the longitudinal and the hyohypoplastral sutures. The length of the anterior lobe 



